2.5-< 3.5         0.09          4.3            2013
                                                              3.5-< 7.0         0.09          4.0            2012
----------------------------------------------------------------------------------------------------------------
\a\ < 75 kW engines at or above 0.9 L/cylinder are subject to the corresponding 75-3700 kW standards.
\b\ Option: 0.15 PM/4.3 NOX+HC in 2014.

                          Table III-6.--Proposed Tier 3 Standards for Marine Diesel C2
----------------------------------------------------------------------------------------------------------------
                                                                                NOX+HC  g/
                       Rated kW                           L/cylinder    PM g/bhp-hr     bhp-hr      Model year
----------------------------------------------------------------------------------------------------------------
=< 3700 kW.............................................           7-< 15         0.10          4.6            2013
                                                                15-< 20     \a\ 0.20      \a\ 6.5            2014
                                                                20-< 25         0.20          7.3            2014
                                                                25-< 30         0.20          8.2            2014
----------------------------------------------------------------------------------------------------------------
\a\ For engines at or below 3300 kW in this group, the PM/NOX+HC Tier 3 standards are 0.25/5.2.

                       Table III-7.--Proposed Tier 4 Standards for Marine Diesel C1 and C2
----------------------------------------------------------------------------------------------------------------
                                                                         NOX g/bhp-
                       Rated kW                           PM g/bhp-hr        hr      HC g/bhp-hr    Model year
----------------------------------------------------------------------------------------------------------------
>3700 kW..............................................        \a\ 0.09          1.3         0.14            2014
                                                                  0.04          1.3         0.14        \b\ 2016
1400-3700 kW..........................................            0.03          1.3         0.14        \c\ 2016
600-< 1400 kW..........................................            0.03          1.3         0.14        \b\ 2017
----------------------------------------------------------------------------------------------------------------
\a\ This standard is 0.19 for engines with 15-30 liter/cylinder displacement.
\b\ Optional compliance start dates are proposed within these model years; see discussion below.
\c\ Option for engines with 7-15 liter/cylinder displacement: Tier 4 PM and HC in 2015 and Tier 4 NOX in 2017.

    The proposed Tier 3 standards for engines with rated power less
than 75 kW (100 hp) are based on the nonroad diesel Tier 2 and Tier 3
standards, because these smaller marine engines are largely derived
from (and often nearly identical to) the nonroad engine designs. The
relatively straightforward carry-over nature of this approach also
allows for an early implementation schedule, model year 2009, providing
substantial early benefits to the program. However, some of the less
than 75 kW nonroad engines are also subject to aftertreatment-based
Tier 4 nonroad standards, and our proposal would not carry these over
into the marine sector, due to vessel design and operational
constraints discussed in Section III.D. Because of the preponderance of
both direct- and indirect-injection diesel engines in the 19 to 75 kW
(25-100 hp) engine market today, we are proposing two options available
to manufacturers for meeting Tier 3 standards on any engine in this
range, as indicated in Table III-4. One option focuses on lower PM and
the other on lower NOX, though both require substantial
reductions in both PM and NOX and would take effect in 2014.
    With important exceptions, we propose that marine diesel engines at
or above 75 kW (100 hp) be subject to new emissions standards in two
steps, Tier 3 and Tier 4. The proposed Tier 3 standards are based on
the engine-out emission reduction potential of the nonroad Tier 4
diesel engines which will be introduced beginning in 2011. Tier 3
standards for C1 engines would generally take effect in 2012, though
for some engines, they would start in 2013 or 2014. We are not basing
our proposed marine Tier 3 emission standards on the existing nonroad
Tier 3 emission standards for two reasons. First, the nonroad Tier 3
engines will be replaced beginning in 2011 with nonroad Tier 4 engines,
and given the derivative nature of marine diesel manufacturing, we
believe it is more appropriate to use those Tier 4 engine capabilities
as the basis for the proposed marine standards. Second, the advanced
fuel and combustion systems that we expect these Tier 4 nonroad engines
to apply will allow approximately a 50 percent reduction in PM when
compared to the reduction potential of the nonroad Tier 3 engines. The
proposed Tier 3 standards levels would vary slightly, from 0.08 to 0.11
g/bhp-hr (0.11 to 0.15 g/kW-hr) for PM and from 4.0 to 4.3 g/bhp-hr
(5.4 to 5.8 g/kW-hr) for NOX+HC. Tier 3 standards for C2
engines would take effect in 2013 or 2014, depending on engine
displacement, and standards levels would also vary, from 0.10 to 0.25
g/bhp-hr (0.14 to 0.34 g/kW-hr) for PM and 4.6 to 8.2 g/bhp-hr (6.2 to
11.0 g/kW-hr) for NOX+HC. For the largest C2 engines, those
above 3700 kW (4900 hp), the NOX+HC standard would remain at
the Tier 2 levels until Tier 4 begins for these engines in 2014.
    We are proposing that high-efficiency aftertreatment-based Tier 4
standards be

applied to all commercial and auxiliary C1 and C2 engines over 600 kW
(800 hp). These standards would phase in over 2014-2017. Marine diesels
over 600 kW, though fewer in number, are the workhorses of the inland
waterway and intercoastal marine industry, running at high load
factors, for many hours a day, over decades of heavy use. As a result
they also account for the very large majority of marine diesel engine
emissions. However, for engines at or below 600 kW, our technical
analysis indicates that applying aftertreatment to them appears at this
time not to be feasible. There are many reasons for this preliminary
conclusion, varying in relative importance with engine size and
application, but generally including insufficient space in below-deck
engine compartments, catalyst packaging limitations for water-injected
exhaust systems, poor catalyst performance in water-jacketed exhaust
systems, and weight constraints in planing hull vessels.
    Although with time and investment these issues may be resolvable
for some under 600 kW (800 hp) applications, we are not, at this time,
proposing Tier 4 standards for these engines. We may do so at some
point in the future, such as after the successful prove-out of
aftertreatment in the larger marine engines and in nonroad diesel
engines have established a clearer technology path for extension to
these engines. The approach taken in this proposal concentrates Tier 4
design and development efforts into the engine and vessel applications
where they can do the most good.
    We are confident that there is a subset of recreational vessels
that are large enough to accommodate the added size of engines equipped
with aftertreatment and that have appropriate maintenance procedures to
ensure that the aftertreatment systems are appropriately maintained,
for example, because they have a professional crew as opposed to being
maintained by the owner. Based on a review of publicly available sales
literature, we believe that at least the subset of recreational vessels
with engines at rated power above 2000 kW (2760 hp) have the space and
design layout conducive to aftertreatment and professional crews such
that aftertreatment-based standards are feasible. Therefore, we are
proposing to apply the Tier 4 standards to recreational marine diesel
engines at rated power above 2000 kW, but we request comment on whether
this is the appropriate threshold, along with any available information
supporting the commenter's view. We also request comment on the issue
of ULSD availability for these vessels in places that they may visit
outside the United States. The rapid pace at which the industrial
nations are shifting to ULSD has surpassed expectations. By no means
does this ensure its availability in every port that might be
frequented by large U.S. yachts, but it does give confidence that ULSD
will be a global product, and certainly not confined to the coastal
U.S. when Tier 4 yachts begin to appear in 2016. These large yachts are
operated by professional crews who plan their itineraries ahead of time
and are unlikely to put in for fuel without checking out the facility
ahead of time, though quite possibly this may require somewhat more
diligence in the early years of the program while the ULSD-needing
fleet is ramping up in size. We also expect that, from the marinas'
perspective, those frequented by these affluent visitors typically
covet this business today, and will likely be reticent to leave ULSD
off the list of offerings and amenities aimed at attracting them.
    We are setting the Tier 4 standards for most engines above 600 kW
(800 hp) at 0.03 g/bhp-hr (0.04 g/kW-hr) for PM, based on the use of PM
filters, and 1.3 g/bhp-hr (1.8 g/kW-hr) for NOX based on the
use of urea SCR systems. The largest marine diesel engines, those above
3700 kW (4900 hp), would be subject to this SCR-based NOX
standard in 2014, along with a new engine-based PM standard. The Tier 4
PM standard for these engines would then start in 2016, with the
addition of a filter-based 0.04 g/bhp-hr (0.06 g/kW-hr) standard. See
section III.C(3) for a discussion of the Tier 4 HC standard.
    Note that the implementation schedule in the above marine standards
tables is expressed in terms of model years, consistent with past
practice and the format of our regulations. However, in two cases we
believe it is appropriate to provide a manufacturer the option to delay
compliance somewhat, as long as the standards are implemented within
the indicated model year. Specifically, we are proposing to allow a
manufacturer to delay Tier 4 compliance within the 2017 model year for
600-1000 kW (800-1300 hp) engines by up to 9 months (but no later than
October 1, 2017) and, for Tier 4 PM, within the 2016 model year for
over 3700 kW (4900 hp) engines by up to 12 months (but no later than
December 31, 2016). We consider this option to delay implementation
appropriate in order to give some flexibility in spreading the
implementation workload and ensure a smooth transition to the long-term
Tier 4 program.
    The proposed Tier 4 standards for locomotives and C2 diesel marine
engines of comparable size are at the same numerical levels but differ
somewhat in implementation schedule, with locomotive Tier 4 starting in
2015 for PM and 2017 for NOX, and diesel marine Tier 4 for
both PM and NOX starting in 2016 (for engines in the 1400-
3700 kW (1900-4900 hp) range). We consider these implementation
schedules to be close enough to warrant our providing an option to meet
either schedule for these marine engines, aimed at facilitating the
development of engines for both markets, a common practice today.
Because the locomotive Tier 4 phase-in is offset by only one year on
either side of the marine Tier 4 2016 date, we do not expect this
option to introduce major competitiveness issues between manufacturers
who will be designing engines for both markets and those who will be
designing for only the marine market. Furthermore, we see no reason to
make this option available only those who make locomotive products, and
are therefore proposing its availability to any manufacturer. Comment
is requested on the need for the option, and on whether it should be
limited to a particular subset of engines.
    We note too that the Tier 3 marine standards for locomotive-like
marine engines (that is, in the 7-15 liters/cylinder group) although
having the same implementation date and numerical PM standard level as
locomotive Tier 3, includes a 4.6 g/bhp-hr (6.1 g/kW-hr)
NOX+HC standard, compared to the 5.5 g/bhp-hr (7.3 g/kW-hr)
NOX standard for locomotive Tier 3. We request comment on
whether some provision is needed to avoid the need for designing an
engine primarily used in locomotives to meet the marine standard in
order to have both ready for Tier 3, on whether sufficient ABT credits
are likely to be available to deal with this, and on how to ensure we
do not lose environmental benefits or inadvertently create
competitiveness problems.
    Some marine engine families include engines of the same basic
design and emissions performance but achieving widely varying power
ratings in engine models marketed through varying the number of
cylinders, for example 8 to 20. These families can and do straddle
power cutpoints, most notably at the 3700 kW (4900 hp) cutpoint, above
which NOX aftertreatment is expected to be needed in 2014
under our proposed standards, and at the 600 kW (800 hp) cutpoint for
application of the proposed Tier 4 standards. We understand that
manufacturers have concerns about additional design and certification
work

needed for an engine family falling into two categories, especially
with regard to the 600 and 3700 kW cutpoints which involve very
different standards or start dates on either side of the cutpoint. We
request comment on whether this concern is a serious one for the
manufacturers, on suggestions for how to address it fairly without a
loss of environmental benefit, and on whether our not addressing it
would cause undesirable shifts in ratings offered in the market in
order to stay on one side or the other of the cutpoints. One particular
idea on which we request comment is allowing engines above 3700 kW an
option to meet the Tier 4 PM requirement in 2014 and the Tier 4
NOX requirement December 31, 2016, similar to the less than
3700 kW option discussed above.
    We are concerned that applying the Tier 4 standards to engines
above 600 kW (800 hp) may create an incentive for vessel builders who
would normally use engines greater than 600 kW to instead use a larger
number of smaller engines in a vessel to get the equivalent power
output. Generally, the choice of engines for a vessel is directly a
function of the work that vessel is intended to do. There may be cases,
however, in which a vessel designer that might have used, for example,
two 630 kW engines, chooses instead to use three 420 kW engines to
avoid the Tier 4 standards. We have concerns about the environmental
impacts of such a result. There also may be competitiveness concerns.
Therefore, we are seeking comment on whether substitution of several
smaller engines for one or two larger engines is likely to occur as a
result of differential standards, and on what can be done to avoid it.
For example, the Tier 4 standards could be applied to engines in multi-
engine vessels with a total power above a certain threshold, such as
1100 kW (1500 hp). We recognize that this would result in a need to
equip engines somewhat below 600 kW with aftertreatment devices, but we
believe the feasibility concerns such as space constraints discussed
above for engines below this cutpoint are diminished in multi-engine
vessel designs. Alternatively, we could require vessel manufacturers
seeking to use more than two engines to make a demonstration to us that
they are not attempting to circumvent the aftertreatment-based
requirements, for example by showing that the vessel design they are
using traditionally incorporates three or more engines or that there is
a specific design requirement that leads to the use of several smaller
engines. A third option would be to base the Tier 4 standards on the
size (or other characteristics) of the vessel, for vessels that have
two or more propulsion engines. Commenters on this issue should address
the feasibility and potential market impacts of these potential
solutions and are asked to offer their own suggestions as well.
(3) Carbon Monoxide, Hydrocarbon, and Smoke Standards
    We are not proposing new standards for CO. Emissions of CO are
typically relatively low in diesel engines today compared to non-diesel
pollution sources. Furthermore, among diesel application sectors,
locomotives and marine diesel engines are already subject to relatively
stringent CO standards in Tier 2--essentially 1.5 and 3.7 g/bhp-hr,
respectively, compared to the current heavy-duty highway diesel engine
CO standard of 15.5 g/bhp-hr. Therefore, under our proposal, the Tier 3
and Tier 4 CO standards for all locomotives and marine diesel engines
would remain at current Tier 2 levels and remanufactured Tier 0, 1 and
2 locomotives would likewise continue to be subject to the existing CO
standards for each of these tiers. Although we are not setting more
stringent standards for CO in Tier 4, we note that aftertreatment
devices using precious metal catalysts that we project will be employed
to meet Tier 4 PM, NOX and HC standards would provide
meaningful reductions in CO emissions as well.
    As discussed in section II, HC emissions, often characterized as
VOCs, are precursors to ozone formation, and include compounds that EPA
considers to be air toxics. As for CO, emissions of HC are typically
relatively low in diesel engines today compared to non-diesel sources.
However, in contrast to CO standards, the line-haul locomotive Tier 2
HC standard of 0.30 g/bhp-hr, though comparable to emissions from other
diesel applications in Tier 2 and Tier 3, is more than twice that of
the long-term 0.14 g/bhp-hr standard set for both the heavy-duty
highway 2007 and nonroad Tier 4 programs. For marine diesel engines the
Tier 2 HC standard is expressed as part of a combined NOX+HC
standard varying by engine size between 5.4 and 8.2 g/bhp-hr, which
clearly allows for high HC levels. Our proposed more stringent Tier 3
NOX+HC standards for marine diesel engines would likely
provide some reduction in HC emissions, but we expect that the
catalyzed exhaust aftertreatment devices used to meet the proposed Tier
4 locomotive and marine NOX and PM standards would
concurrently provide very sizeable reductions in HC emissions.
Therefore, in accordance with the Clean Air Act section 213 provisions
outlined in section I.B(3) of this preamble, we are proposing that the
0.14 g/hp-hr HC standard apply for locomotives and marine diesel
engines in Tier 4 as well.
    We are proposing that the existing form of the HC standards be
retained through Tier 3. That is, locomotive and marine HC standards
would remain in the form of total hydrocarbons (THC), except for
gaseous- and alcohol-fueled engines (See 40 CFR Sec.  92.8 and Sec.
94.8). Consistent with this, the Tier 3 marine NOX+HC
standards are proposed to be based on THC, except that Tier 3 standards
for less than 75 kW (100 hp) engines would be based on NMHC, consistent
with their basis in the nonroad engine program. However, we propose
that the Tier 4 HC standards be expressed as NMHC standards, consistent
with aftertreatment-based standards adopted for highway and nonroad
diesel engines.
    As in the case of other diesel mobile sources, we believe that
existing smoke standards are of diminishing usefulness as PM levels
drop to very low levels, as engines with PM at these levels emit very
little or no visible smoke. We are therefore proposing to drop the
smoke standards for locomotives and marine engines for any engines
certified to a PM family emission limit (FEL) or standard of 0.05 g/
bhp-hr (0.07 g/kW-hr) or lower. This allows engines certified to Tier 4
PM or to an FEL slightly above Tier 4 to avoid unnecessary testing for
smoke.

D. Are the Proposed Standards Feasible?

    In this section we describe the feasibility of the various
emissions control technologies we project would be used to meet the
standards proposed today. Because of the range of engines and
applications we cover in this proposal, and because of the technology
that will be available to them for emissions control, our proposed
standards span a range of emissions levels. We have identified a number
of different emissions control technologies we would expect to be used
to meet the proposed standards. These technologies range from
incremental improvements to existing engine components for the proposed
remanufacturing program to highly advanced catalytic exhaust treatment
systems similar to those expected to be used to control emissions from
heavy-duty diesel trucks and nonroad equipment.
    In this section we first describe the feasibility of emissions
control technologies we project would be used

to meet the standards we are proposing for existing engines that are
remanufactured as new (i.e., Tier 0, Tier 1, Tier 2). We also describe
how these same technologies would be applied to meet our proposed
interim standards for new engines (i.e., Tier 3). We conclude this
section with a discussion of catalytic exhaust treatment technologies
projected to be used to meet our proposed Tier 4 standards. A more
detailed analysis of these technologies and the issues related to their
application to locomotive and marine diesel engines can be found in the
draft Regulatory Impact Analysis (RIA).
(1) Emissions Control Technologies for Remanufactured Engine Standards
and for New Tier 3 Engine Standards
    In the locomotive sector, emissions standards already exist for
engines that are remanufactured as new. Some of these engines were
originally unregulated (i.e. Tier 0), and others were originally built
to earlier emissions standards (Tier 1 and Tier 2). We are proposing
more stringent standards for these engines that apply whenever the
locomotives are remanufactured as new. Our proposed remanufactured
standards apply to locomotive engines that were originally built as
early as 1973.
    We project that incremental improvements to existing engine
components would be feasible to meet our proposed locomotive
remanufactured engine standards. In many cases, similar improvements to
these have already been implemented on newly built locomotives to meet
our current new locomotive standards. To meet the lower NOX
standard proposed for the Tier 0 locomotive remanufacturing program, we
expect that improvements in fuel system design, engine calibration and
optimization of existing after-cooling systems may be used to reduce
NOX from the current 9.5 g/bhp-hr Tier 0 standard to 7.4 g/
bhp-hr. These are the same technologies used to meet the current Tier 1
NOX emission standard of 7.4 g/bhp-hr. In essence,
locomotive manufacturers will duplicate current Tier 1 locomotive
NOX emission solutions and adapt those same solutions to the
portion of the existing Tier 0 fleet that can accommodate them. For
older Tier 0 locomotives manufactured without separate-circuit cooling
systems for intake air charge air cooling, reaching the Tier 1
NOX level will not be possible. For these engines 8.0 g/hp-
hr NOX emissions represents the lowest achievable level.
    To meet all of our proposed PM standards for the remanufacturing
program and for the new locomotive Tier 3 interim standard, we expect
that lubricating oil consumption controls will be implemented, along
with the ultra low sulfur diesel fuel requirement for locomotive
engines (which was previously finalized in our nonroad clean diesel
rulemaking). Because of the significant fraction of lubricating oil
present in PM from today's locomotives, we believe that existing low-
oil-consumption piston ring-pack designs, when used in conjunction with
improvements to closed crankcase ventilation systems, will provide
significant, near-term PM reductions. These technologies can be applied
to all locomotive engines, including those built as far back as 1973.
And based upon our on-highway and nonroad clean diesel experience, we
also believe that the use of ultra low sulfur diesel fuel in the
locomotive sector will assist in meeting the Tier 2 remanufacturing and
Tier 3 PM standards. We believe that the combination of reduced sulfate
PM and improvement of oil and crankcase emission control to near Tier 3
nonroad or 2007 heavy-duty on-highway levels will provide an
approximately 50% reduction in PM emissions.
    We believe that some fraction of the remanufacturing systems can be
developed and certified as early as 2008, so we are proposing the
required usage of Tier 0, Tier 1 and Tier 2 emission control systems as
soon as they are available starting in 2008. However, we estimate that
it will take approximately 3 years to complete the development and
certification process for all of the Tier 0 and Tier 1 emission control
systems, so we have proposed full implementation of the Tier 0 and Tier
1 remanufactured engine standards in 2010. We base this lead time on
the types of technology that we expect to be implemented, and on the
amount of lead time locomotive manufacturers needed to certify similar
systems for our current remanufacturing program. The new engine changes
necessary to meet the Tier 3 and remanufactured Tier 2 PM emission
standards will require additional engine changes leading us to propose
an implementation date for those engines of 2012 for Tier 3 engines and
2013 for remanufactured Tier 2 engines. These changes include further
improvements to ring pack designs--especially for two-stroke engines,
and the implementation of high efficiency crankcase ventilation
systems. These technologies are described and illustrated in detail in
our draft Regulatory Impact Analysis.
    In the marine sector, emissions standards do not currently exist
for engines that are remanufactured as new. In today's proposal, we are
requesting comment on a marine diesel engine remanufacturing program
that would apply to some of these marine engines whenever they are
remanufactured as new (see section VII.A(2)). Because we are requesting
comment on a marine engine remanufacturing program that essentially
parallels our locomotive remanufacturing program, we expect that the
same emissions control technologies described above would be
implemented for remanufactured marine diesel engines just as for
remanufactured locomotive engines.
    We are proposing more stringent emissions standards for all newly
built marine diesel engines that have a displacement of less than
thirty liters per cylinder. For marine diesel engines that are either
used in recreational vessels or are rated to produce less than 600 kW
of power, we are proposing emissions standards that likely would not
require the use of catalytic exhaust treatment technology. We are also
proposing similar standards, as interim standards, for marine diesel
engines that are used in commercial vessels and are rated to produce
600 kW of power or more (except if greater than 3700 kW). Collectively,
we refer to these standards as our Tier 3 marine diesel engine
standards.
    To meet our proposed Tier 3 marine diesel engine standards, we
believe that engine manufacturers will utilize incremental improvements
to existing engine components. To meet the lower NOX
standards we expect that improvements in fuel system design and engine
calibration will be implemented. For Category 1 engines from 75 kW
through 560 kW, these technologies would be similar to designs and
calibrations that likely will be used to meet our nonroad Tier 4
standards for engines. For Category 1 engines below 75 kW and greater
than 560kW, and for Category 2 engines that have cylinder displacements
less than 15 L/cylinder, these technologies are similar to designs that
will be used to meet our nonroad Tier 3 standards, and our proposed
locomotive Tier 3 standards.
    In almost all instances, marine diesel engines are derivative of
land based nonroad engines or locomotive engines. In order to meet our
nonroad Tier 4 emission levels (phased in from 2011-2015), nonroad
engines will see significant base engine improvements designed to
reduce engine-out emissions. Refer to our nonroad Tier 4 rulemaking for
details on the designs and calibrations we expect to be used to meet
the Tier 3 standards we are proposing for the lower horsepower marine
engines. For example, we expect

marine engines to utilize high-pressure, common-rail fuel injection
systems or improvements in unit injector design. When such fuel system
improvements are used in conjunction with engine mapping and
calibration optimization, the Tier 3 marine diesel engine standards can
be met. Since this technology and these components already have been
implemented on on-highway, nonroad, and some locomotive engines, they
can be applied to marine engines beginning as early as 2009.
    Because some marine engines are not as similar to on-highway,
nonroad or locomotive engines as others, we believe that full
implementation of these technologies for marine engines cannot be
accomplished until 2012. We expect that the PM emissions control
technologies that will be used to meet our proposed Tier 3 marine
diesel engine standards will be similar to the technology used to meet
our nonroad Tier 3 PM standards and our proposed locomotive Tier 3 PM
standards. That is, we believe that a combination of fuel injection
improvements, plus the use of existing low-oil-consumption piston ring-
pack designs and improved closed crankcase ventilation systems will
provide significant PM reductions. And based upon our on-highway and
non-road clean diesel experience, we also believe that the use of ultra
low sulfur diesel fuel in the marine sector will assist in meeting the
Tier 3 PM standards.
    Because all of the aforementioned technologies to reduce
NOX and PM emissions can be developed for production,
certified, and introduced into the marine engine sector without
extended lead-time, we believe that these technologies can be
implemented for some engines as early as 2009, and for all engines by
2014. We believe that this later date is needed only for those marine
engines that are not similar to other on-highway, nonroad, or
locomotive engines.
(2) Catalytic Exhaust Treatment Technologies for New Engines
    For marine diesel engines in commercial service that are greater
than 600 kW, for all marine engines greater than 2000 kW, and for all
locomotives, we are proposing stringent Tier 4 standards based on the
use of advanced catalytic exhaust treatment systems to control both PM
and NOX emissions. There are four main issues to address
when analyzing the application of this technology to these new sources:
the efficacy of the fundamental catalyst technology in terms of the
percent reduction in emissions given certain engine conditions such as
exhaust temperature; its applicability in terms of packaging; its long-
term durability; and whether or not the technology significantly
impacts an industry's supply chain infrastructure--especially with
respect to supplying urea reductant for SCR to locomotives and vessels.
We have carefully examined these points, and based upon our analysis
(detailed in our draft Regulatory Impact Analysis), we believe that we
have identified robust PM and NOX catalytic exhaust
treatment systems that are applicable to locomotives and marine engines
that also pose a manageable impact on the rail and marine industries'
infrastructure.
(a) Catalytic PM Emissions Control Technology
    The most effective exhaust aftertreatment used for diesel PM
emissions control is the diesel particulate filter (DPF). More than a
million light diesel vehicles that are OEM-equipped with DPF systems
have been sold in Europe, and over 200,000 DPF retrofits to diesel
engines have been conducted worldwide.\103\ Broad application of
catalyzed diesel particulate filter (CDPF) systems with greater than 90
percent PM control is beginning with the introduction of 2007 model
year heavy-duty diesel trucks in the United States. These systems use a
combination of both passive and active soot regeneration. CDPF systems
utilizing metal substrates are a further development that trades off a
degree of elemental carbon soot control for reduced backpressure,
improvements in the ability of the trap to clear oil ash, greater
design freedom regarding filter size/shape, and greater robustness.
Metal-CDPFs were initially introduced as passive-regeneration retrofit
technologies for diesel engines designed to achieve approximately 60
percent control of PM emissions. Recent data from further development
of these systems for Euro-4 truck applications has shown that metal-
CDPF trapping efficiency for elemental carbon PM can exceed 70 percent
for engines with inherently low elemental carbon emissions.\104\ Data
from locomotive testing confirms a relatively low elemental carbon
fraction and relatively high organic fraction for PM emissions from
medium-speed Tier 2 locomotive engines.\105\ The use of an oxidizing
catalyst with platinum group metals (PGM) coated directly to the CPDF
combined with a diesel oxidation catalyst (DOC) mounted upstream of the
CDPF would provide 95 percent or greater removal of HC, including the
semi-volatile organic compounds that contribute to PM. Such systems
would reduce overall PM emissions from a locomotive or marine diesel
engine by upwards of 90 percent.
---------------------------------------------------------------------------

    \103\ ``Diesel Particulate Filter Maintenance: Current Practices
and Experience'', Manufacturers of Emission Controls Association,
June 2005, http://meca.org/galleries/default-file/Filter_Maintenance_White_Paper_605_final.pdf
.

    \104\ Jacob, E., L[auml]mmerman, R., Pappenheimer, A., Rothe, D.
``Exhaust Gas Aftertreatment System for Euro 4 Heavy-duty Engines'',
MTZ, June, 2006.
    \105\ Smith, B., Sneed, W., Fritz, S. ``AAR Locomotive Emissions
Testing 2005 Final Report''.
---------------------------------------------------------------------------

    We believe that locomotive and marine diesel engine manufacturers
will benefit from the extensive development taking place to implement
DPF technologies in advance of the heavy-duty truck and nonroad PM
standards in Europe and the U.S. Given the steady-state operating
characteristics of locomotive and marine engines, DPF regeneration
strategies will certainly be capable of precisely controlling PM under
all conditions and passively regenerating whenever the exhaust gas
temperature is >250 [deg]C. Therefore, we believe that the Tier 4 PM
standards we are proposing for locomotive and marine diesel engines are
technologically feasible. And given the level of activity in the on-
highway and nonroad sectors to implement DPF technology, we believe
that our proposed implementation dates for locomotive and marine diesel
engines are appropriate and achievable.
(b) Catalytic NOX Emissions Control Technology
    We have analyzed a variety of technologies available for
NOX reduction to determine their applicability to diesel
engines in the locomotive and marine sectors. As described in more
detail in our draft RIA, we are assuming locomotive and marine diesel
engine manufacturers will choose to use--Selective Catalytic Reduction,
or SCR to comply with our proposed standards. SCR is a commonly used
aftertreatment device for meeting stricter NOX emissions
standards in diesel applications worldwide. Stationary power plants
fueled with coal, diesel, and natural gas have used SCR for three
decades as a means of controlling NOX emissions, and
currently, European heavy-duty truck manufacturers are using this
technology to meet Euro 5 emissions limits. To a lesser extent, SCR has
been introduced on diesel engines in the U.S. market, but the
applications have been limited to marine ferryboat and stationary
electrical power generation demonstration projects in California and

several of the Northeast states. However, by 2010, when 100 percent of
the heavy-duty diesel trucks are required to meet the NOX
limits of the 2007 heavy-duty highway rule, several heavy-duty truck
engine manufacturers have indicated that they will use SCR
technology.\106\ \107\ While other promising NOX-reducing
technologies such as lean NOX catalysts, NOX
adsorbers, and advanced combustion control continue to be developed
(and may be viable approaches to the standards we are proposing today),
our analysis assumes that SCR will be the technology of choice in the
locomotive and marine diesel engine sectors.
---------------------------------------------------------------------------

    \106\ ``Review of SCR Technologies for Diesel Emission Control:
European Experience and Worldwide Perspectives,'' presented by Dr.
Emmanuel Joubert, 10th DEER Conference, July 2004.
    \107\ Lambert, C., ``Technical Advantages of Urea SCR for Light-
Duty and Heavy-Duty Diesel Vehicle Applications,'' SAE Technical
Paper 2004-01-1292, 2004.
---------------------------------------------------------------------------

    An SCR catalyst reduces nitrogen oxides to elemental nitrogen
(N2) and water by using ammonia (NH3) as the
reducing agent. The most-common method for supplying ammonia to the SCR
catalyst is to inject an aqueous urea-water solution into the exhaust
stream. In the presence of high-temperature exhaust gasses (>200
[deg]C), the urea hydrolyzes to form NH3 and CO2.
The NH3 is stored on the surface of the SCR catalyst where
it is used to complete the NOX-reduction reaction. In
theory, it is possible to achieve 100 percent NOX conversion
if the NH3-to-NOX ratio ([alpha]) is 1:1 and the
space velocity within the catalyst is not excessive. However, given the
space limitations in packaging exhaust aftertreatment devices in mobile
applications, an [alpha] of 0.85-1.0 is often used to balance the need
for high NOX conversion rates against the potential for
NH3 slip (where NH3 passes through the catalyst
unreacted). The urea dosing strategy and the desired [alpha] are
dependent on the conditions present in the exhaust gas; namely
temperature and the quantity of NOX present (which can be
determined by engine mapping, temperature sensors, and NOX
sensors). Overall NOX conversion efficiency, especially
under low-temperature exhaust gas conditions, can be improved by
controlling the ratio of two NOX species within the exhaust
gas; NO2 and NO. This can be accomplished through use of an
oxidation catalyst upstream of the SCR catalyst to promote the
conversion of NO to NO2. The physical size and catalyst
formulation of the oxidation catalyst are the principal factors that
control the NO2-to-NO ratio, and by extension, improve the
low-temperature performance of the SCR catalyst.
    Recent studies have shown that an SCR system is capable of
providing well in excess of 80 percent NOX reduction
efficiency in high-power, diesel applications.\108110\ SCR catalysts
can achieve significant NOX reduction throughout much of the
exhaust gas temperature operating range observed in locomotive and
marine applications. Collaborative research and development activities
between diesel engine manufacturers, truck manufacturers, and SCR
catalyst suppliers have also shown that SCR is a mature, cost-effective
solution for NOX reduction on diesel engines in other mobile
sources. While many of the published studies have focused on highway
truck applications, similar trends, operational characteristics, and
NOX reduction efficiencies have been reported for marine and
stationary applications as well.\111\ Given the preponderance of
studies and data--and our analysis summarized here and detailed in the
draft RIA--we believe that this technology is appropriate for
locomotive and marine diesel applications. Furthermore, we believe that
locomotive and marine diesel engine manufacturers will benefit from the
extensive development taking place to implement SCR technologies in
advance of the heavy-duty truck NOX standards in Europe and
the U.S. The urea dosing systems for SCR, already in widespread use
across many different diesel applications, are expected to become more
refined, robust, and reliable in advance of our proposed Tier 4
locomotive and marine standards. Given the steady-state operating
characteristics of locomotive and marine engines, SCR NOX
control strategies will certainly be capable of precisely controlling
NOX under all conditions whenever the exhaust gas
temperature is greater than 150 [deg]C.
---------------------------------------------------------------------------

    \108\ Walker, A.P. et al., ``The Development and In-Field
Demonstration of Highly Durable SCR Catalyst Systems,'' SAE 2004-01-
1289.
    \109\ Conway, R. et al., ``Combined SCR and DPF Technology for
Heavy Duty Diesel Retrofit,'' SAE Technical Paper 2005-01-1862,
2005.
    \110\ ``The Development and On-Road Performance and Durability
of the Four-Way Emission Control SCRTTM System,'' presented by Andy
Walker, 9th DEER Conference, August 28, 2003.
    \111\ Telephone conversation with Gary Keefe, Argillon, June 6,
2006.
---------------------------------------------------------------------------

    To ensure that we have the most up-to-date information on urea SCR
NOX technologies and their application to locomotive and
marine engines, we have met with a number of locomotive and marine
engine manufacturers, as well as manufacturers of catalytic
NOX emissions control systems. Through our discussions we
have learned that some engine manufacturers currently perceive some
risk regarding urea injection accuracy and long-term catalyst
durability, both of which could result in either less efficient
NOX reduction or ammonia emissions. We have carefully
investigated these issues, and we have concluded that accurate urea
injection systems and durable catalysts already exist and have been
applied to urea SCR NOX emissions control systems that are
similar to those that we expect to be implemented in locomotive and
marine applications.
    Urea injection systems applied to on-highway diesel trucks and
diesel electric power generators already ensure accurate injection of
urea, and these applications have similar--if not more dynamic--engine
operation as compared to locomotive and marine engine operation. To
ensure accurate urea injection across all engine operating conditions,
these systems utilize NOX sensors to maintain closed-loop
feedback control of urea injection. These NOX sensor-based
feedback control systems are similar to oxygen sensor-based systems
that are used with catalytic converters on virtually every gasoline
vehicle on the road today. We believe these NOX sensor based
control systems are directly applicable to locomotive and marine
engines.
    Ammonia emissions, which are already minimized through the use of
closed-loop feedback urea injection, can be all-but-eliminated with an
oxidation catalyst downstream of the SCR catalyst. Such catalysts are
in use today and have been shown to be 95% effective at reducing
ammonia emissions.
    Catalyst durability is affected by sulfur and other chemicals that
can be present in some diesel fuel and lubricating oil. These chemicals
have been eliminated in other applications by the use of ultra-low
sulfur diesel fuel and low-SAPS (sulfated ash, phosphorous, and sulfur)
lubricating oil. Locomotive and marine operators already will be using
ultra low sulfur diesel by the time urea NOX SCR systems
would be needed, and low SAPS oil can be used in locomotive and marine
engines. Thermal and mechanical vibration durability of catalysts has
been addressed through the selection of proper materials and the design
of support and mounting structures that are capable of withstanding the
shock and vibration levels present in locomotive and marine
applications. More details on catalyst durability and urea injection
accuracy are available in the remainder of this section and also in our
draft RIA.

    Even though we believe that the issues of catalyst durability and
urea injection accuracy have been addressed in existing NOX
SCR emissions control systems, we invite comments and the submission of
additional information and data regarding catalyst durability and urea
injection accuracy.
(c) Durability of Catalytic PM and NOX Emissions Control
Technology
    Published studies indicate that SCR systems should experience very
little deterioration in NOX conversion throughout the life-
cycle of a diesel engine.\112\ The principal mechanism of deterioration
in an SCR catalyst is thermal sintering--the loss of catalyst surface
area due to the melting and growth of active catalyst sites under high-
temperature conditions (as the active sites melt and combine, the total
number of active sites at which catalysis can occur is reduced). This
effect can be minimized by design of the SCR catalyst washcoat and
substrate for the exhaust gas temperature window in which it will
operate. Another mechanism for catalyst deterioration is catalyst
poisoning--the plugging and/or chemical de-activation of active
catalytic sites. Phosphorus from the engine oil and sulfur from diesel
fuel are the primary components in the exhaust stream which can de-
activate a catalytic site. The risk of catalyst deterioration due to
sulfur poisoning will be all but eliminated with the 2012
implementation of ULSD fuel (< 15 ppm S) for locomotive and marine
applications. Catalyst deterioration due to phosphorous poisoning can
be reduced through the use of engine oil with low sulfated-ash,
phosphorus, and sulfur content (low-SAPS oil) and through reduced
engine oil consumption. The high ash content in current locomotive and
marine engine oils is related to the need for a high total base number
(TBN) in the oil formulation. Because today's diesel fuel has
relatively high sulfur levels, a high TBN in the engine oil is
necessary today to neutralize the acids created when fuel-borne sulfur
migrates to the crankcase. With the use of ULSD fuel, acid formation in
the crankcase will not be a significant concern. The low-SAPS oil will
be available for on-highway use by October 2006 and is specified by the
American Petroleum Institute as ``CJ-4.'' We also expect that Tier 3
locomotive and marine engine designs will have reduced oil consumption
in order to meet the Tier 3 PM standards, and that the Tier 4 designs
will be an evolutionary development that will apply catalytic exhaust
controls to the Tier 3 engine designs. The durability of other exhaust
aftertreatment devices, namely the DOC and CDPF, will also benefit from
the use of ULSD fuel, reduced oil consumption and low-SAPS engine oil
because the reduction in exposure of these devices to sulfur and
phosphorous will improve their effectiveness and the reduction in ash
loading will increase the CDPF ash-cleaning intervals.
---------------------------------------------------------------------------

    \112\ Conway, R. et al., ``NOX and PM Reduction Using
Combined SCR and DPF Technology in Heavy Duty Diesel Applications,''
SAE Technical Paper 2005-01-3548, 2005.
---------------------------------------------------------------------------

(d) Packaging of Catalytic PM and NOX Emissions Control
Technology
    We project that locomotive manufacturers will need to re-package/
re-design the exhaust system components to accommodate the
aftertreatment system. Our analysis shows the packaging requirements
for the aftertreatment system are such that they can be accommodated
within the envelope defined by the Association of American Railroads
(AAR) Plate ``L'' clearance diagram for freight locomotives.\113\
Typical volume required for the SCR catalyst and post-SCR ammonia slip
catalyst for Euro V and U.S. 2010 heavy-duty truck applications is
approximately 2 times the engine displacement, and the upstream DOC/
CDPF volume is approximately 1-1.5 times the engine displacement. Due
to the longer useful life and maintenance intervals required for
locomotive applications, we estimate that the SCR catalyst volume will
be sized at approximately 2.5 times the engine displacement, and the
combined DOC/CDPF volume will be approximately 1.7 times the engine
displacement. For an engine with 6 ft\3\ of total displacement, the
volume requirement for the aftertreatment components would be
approximately 25 ft\3\. EPA engineers have examined Tier 2 EMD and GE
line-haul locomotives and conclude that there is adequate space to
package these components. This conclusion also applies to new switcher
locomotives, which, while being shorter in length than line-haul
locomotives, will also be equipped with smaller, less-powerful
engines--resulting in smaller volume requirements for the
aftertreatment components. Given the space available on today's
locomotives, we feel that packaging catalytic PM and NOX
emissions control technology on-board locomotives is actually less
challenging than packaging similar technology on-board other mobile
sources such as light-duty vehicles, heavy-duty trucks, and nonroad
equipment. Given that similar exhaust systems are either already
implemented on-board these vehicles or will be implemented on these
vehicles years before similar systems would be required on-board
locomotives, we believe that any packaging issues would be successfully
addressed early in the locomotive redesign process.
---------------------------------------------------------------------------

    \113\ ``AAR Manual of Standards and Recommended Practices,''
Standard S-5510, Association of American Railroads.
---------------------------------------------------------------------------

    For commercial vessels that use marine diesel engines greater than
600 kW, we expect that marine vessel builders will need to re-package
and re-design the exhaust system components to accommodate the
aftertreatment components expected to be necessary to meet the proposed
standards. Our discussions with marine architects and engineers, along
with our review of vessel characteristics, leads us to conclude for
commercial marine vessels, adequate engine room space can be made
available to package aftertreatment components. Packaging of these
components, and analyzing their mass/placement effect on vessel
characteristics, will become part of the design process undertaken by
marine architecture firms.\114\
---------------------------------------------------------------------------

    \114\ Telephone conversation between Brian King, Elliot Bay
Design Group, and Brian Nelson, EPA, July 24, 2006.
---------------------------------------------------------------------------

    We did determine, however, that for recreational vessels and for
vessels equipped with engines less than 600 kW, catalytic PM and
NOX exhaust treatment systems were less practical from a
packaging standpoint than for the larger, commercially operated
vessels. We did identify catalytic emissions control systems that would
significantly reduce emissions from these smaller vessels. However,
after taking into consideration costs, energy, safety, and other
relevant factors, we identified a number of reasons why we are not
proposing at this time any standards that would likely require
catalytic exhaust treatment systems on these smaller vessels. One
reason is that most of these vessels use seawater (fresh or saltwater)
cooled exhaust systems, and even seawater injection into their exhaust
systems, to cool engine exhaust to prevent overheating materials such
as a fiberglass hull. This current practice of cooling and seawater
injection could reduce the effectiveness of catalytic exhaust treatment
systems. This is significantly more challenging than for gasoline
catalyst systems due to much larger relative catalyst sizes and cooler
exhaust temperatures typical of diesel engines. In addition, because of
these

vessels' small size and their typical design to operate by planing high
on the surface of the water, catalytic exhaust treatment systems pose
several significant packaging and weight challenges. Normally, such
packaging and weight challenges would be addressed by the use of
lightweight hull and superstructure materials. However, the currently
accepted lightweight vessel materials are incompatible with the
temperatures required to sustain catalyst effectiveness. One solution
could be new lightweight hull and superstructure materials which would
have to be developed, tested and approved prior to their application on
vessels using catalytic exhaust treatment systems. Given these issues,
we believe it is prudent to not propose catalytic exhaust treatment-
based emission standards for marine diesel engines below 600 kW at this
time.
(e) Infrastructure Impacts of Catalytic PM and NOX Emissions
Control Technology
    For PM trap technology the locomotive and marine industries will
have minimal impact imposed upon their industries' infrastructures.
Since PM trap technology relies on no separate reductant, any
infrastructure impacts would be limited to some minor changes in
maintenance practices or maintenance facilities. Such maintenance would
be limited to the infrequent process of removing lubricating oil ash
buildup from within a PM trap. This type of maintenance might require
facilities to remove PM traps for cleaning. This might involve the use
of a crane or other lifting device. We understand that much of this
kind of infrastructure already exists for other locomotive and marine
engine maintenance practices. We have toured shipyards and locomotive
maintenance facilities at rail switchyards, and we observed that such
facilities are generally already adequate for any required PM trap
maintenance.
    We do expect some impact on the railroad and marine sectors to
accommodate the use of a separate reductant for use in a NOX
SCR system. For light-duty, heavy-duty, and nonroad applications, the
preferred reductant in an SCR system is a 32.5 percent urea-water
solution. The 32.5 percent solution, also known as the ``eutectic''
concentration, provides the lowest freezing point (-11 [deg]C or 12
[deg]F) and assures that the ratio of urea-to-water will not change
when the solution begins to freeze.\115\ Heated storage tanks and
insulated dispensing equipment may be necessary to prevent freeze-up in
Northern climates. In addition, the urea dosing apparatus (urea storage
tank, pump, and lines) onboard the locomotive or marine vessel may
require similar protections. Locomotives and marine vessels are
commonly refueled from large, centralized fuel storage tanks, tanker
trucks, or tenders with long-term purchase agreements. Urea suppliers
will be able to distribute urea to the locomotive and marine markets in
a similar manner, or they may choose to employ multi-compartment diesel
fuel/urea tanker trucks for delivery of both products simultaneously.
The frequency that urea needs to be added will be dependent on the urea
storage capacity, duty-cycle, and urea dosing rate for each
application. Discussions concerning the urea infrastructure in North
America and specifications for an emissions-grade urea solution are now
under way amongst light- and heavy-duty on-highway diesel stakeholders.
---------------------------------------------------------------------------

    \115\ Miller, W. et al., ``The Development of Urea-SCR
Technology for U.S. Heavy Duty Trucks,'' SAE Technical Paper 2000-
01-0190, 2000.
---------------------------------------------------------------------------

    Although an infrastructure for widespread transportation, storage,
and dispensing of SCR-grade urea does not currently exist in the U.S.,
the affected stakeholders in the light- and heavy-duty on-highway and
nonroad diesel sectors are expected to follow the European model, in
which diesel engine/truck manufacturers and fuel refiners/distributors
formed a collaborative working group known as ``AdBlue.'' The goal of
the AdBlue organization is to resolve potential problems with the
supply, handling, and distribution of urea and to establish standards
for product purity.\116\ Concerning urea production capacity, the U.S.
has more-than-sufficient capacity to meet the additional needs of the
rail and marine industries. For example, in 2003, the total diesel fuel
consumption for Class I railroads was approximately 3.8 billion
gallons.\117\ If 100 percent of the Class I locomotive fleet were
equipped with SCR catalysts, approximately 190 million gallons-per-year
of 32.5 percent urea-water solution would be required.\118\ It is
estimated that 190 million gallons of urea solution would require 0.28
million tons of dry urea (1 ton dry urea is needed to produce 667
gallons of 32.5 percent urea-water solution). Currently, the U.S.
consumes 14.7 million tons of ammonia resources per year, and relies on
imports for 41 percent of that total (of which, urea is the principal
derivative). In 2005 domestic ammonia producers operated their plants
at 66 percent of rated capacity, resulting in 4.5 million tons of
reserve production capacity.\119\ In the hypothetical situation above,
where 100 percent of the locomotive fleet required urea, only 6.2
percent of the reserve domestic capacity would be needed to satisfy the
additional demand. A similar analysis for the marine industry, with a
yearly diesel fuel consumption of 2.2 billion gallons per year, would
not significantly impact the urea demand-to-reserve capacity equation.
Since the rate at which urea-SCR technology is introduced to the
railroad and marine markets will be gradual--and the reserve urea
production capacity is more-than-adequate to meet the expected demand
in the 2017 timeframe--EPA does not project any urea cost or supply
issues will result from implementing the proposed Tier 4 standards.
---------------------------------------------------------------------------

    \116\ ``Ensuring the Availability and Reliability of Urea Dosing
for On-Road and Non-Road,'' presented by Glenn Barton, Terra Corp.,
9th DEER Conference, August 28, 2003.
    \117\ ``National Transportation Statistics--2004,'' Table 4-5,
U.S. Bureau of Transportation Statistics.
    \118\ Assuming the dosing rate of 32.5 percent urea-water
solution is 5 percent of the total fuel consumed; 3.8 billion
gallons of diesel fuel * 0.05 = 190 million gallons of urea-water
solution.
    \119\ ``Mineral Commodity Summaries 2006,'' page 118, U.S.
Geological Survey, http://www.minerals.usgs.gov/minerals/pubs/mcs/mcs2006.pdf
.

---------------------------------------------------------------------------

(3) The Proposed Standards Are Technologically Feasible
    Our proposal covers a wide range of engines and the implementation
of a range of emissions controls technologies, and we have identified a
range of technologically feasible emissions control technologies that
likely would be used to meet our proposed standards. Some of these
technologies are incremental improvements to existing engine
components, and many of these improved components have already been
applied to similar engines. The other technologies we identified
involve catalytic exhaust treatment systems. For these technologies we
carefully examined the catalyst technology, its applicability to
locomotive and marine engine packaging constraints, its durability with
respect to the lifetime of today's locomotive and marine engines, and
its impact on the infrastructure of the rail and marine industries.
From our analysis, which is presented in detail in our draft RIA, we
conclude that incremental improvements to engine components and the
implementation of catalytic PM and NOX exhaust treatment
technology would be feasible to meet our proposed emissions standards.

(4) A Request for Detailed Technical Comments
    We have carried out an extensive outreach program with the
regulated industry to understand the potential impacts and technical
challenges to the application of aftertreatment technology to diesel
locomotives and marine engines. We are requesting comments on all parts
of our resulting analyses summarized in the preceding sections and
presented in greater detail in the Draft RIA.
    Further, we request comment on the following list of detailed
questions provided to the Agency by a stakeholder regarding particular
challenges in applying aftertreatment technologies to diesel
locomotives. Some of these questions raise concerns about the
feasibility of the proposed Tier 4 standards under specific
environmental conditions. We present theses questions without endorsing
the appropriateness of applying these conditions to locomotive catalyst
designs. The reader should refer to the preceding sections and the
draft RIA for our analyses of the relevant issues.
    (1) How do the following attributes of the locomotive exhaust
environment impact the ability of a Zeolite SCR type catalyst to
operate within 10% of its ``as new'' conversion efficiency (~94%) after
34,000 MW-hours of operation?
    [cir] 150 hours per year operation at 600 Celsius exhaust
temperature at the inlet to the SCR, due to DPF regeneration.'' (20-
minute regeneration every 20 hours of operation).
    [cir] 120 minutes per year operation at 700 Celsius.
    [cir] Soot exposure equal to 0.03 g/bhp-hr.
    [cir] Shock loading averaging 1,000 mechanical shock pulses per
year due to hard coupling.
    [cir] Extended periods of vibration where the vibration load on the
catalysts can reach 6G and 1000 Hz.
    [cir] Water exposure due to rains, icing, water spray and condensed
frozen or liquid water during 20% of its life.
    [cir] Salt fog consisting of 5  1% salt concentration
by weight with fallout rate between 0.00625 and 0.0375 ml/cm\2\/hr.
    [cir] The catalysts will be subject to sands composed of 95% of
SiO2 with particle size between 1 to 650 microns in diameter
with sand concentration of 1.1  0.25 g/m\3\ and air
velocity of 29 m/s (104 km/h).
    [cir] Exposure to dusts comprised of red china clay and silicon
flour of particle sizes that are between 1 to 650 microns in diameter
with dust concentration of 10.6  7 g/m\3\ with a velocity
equal to locomotive motion velocity on catalyst surfaces.
    (2) Is it feasible for a Zeolite SCR catalyst (as compared to the
Vanadium-based catalysts) to operate within 10% of its as new
conversion efficiency (~94%) after sustained exposure to real exhaust?
If it is, why is it feasible? If it is not feasible, please explain why
it is not.
    (3) Is it feasible to maintain the conversion efficiency of a
diesel oxidation catalyst at least at 45% in the same catalyst
environment described in (1) above? In your comments, please explain
why or why not.
    (4) The feasibility of achieving low ammonia slip, i.e., less than
5 ppm, from urea-based SCR systems that dose at or above 1:1 ratios
when applied to an exhaust stream with 500-600 ppm NOX under
both steady state and transient load conditions.
    (5) The feasibility of a reliable NOX sensor with 5%
accuracy to control urea dosing sufficiently to achieve a 95%
NOX conversion efficiency using a Zeolite-based SCR when not
kinetically limited.
    (6) The expected level of ammonia slip catalyst selectivity back to
NOX when a Zeolite-based SCR is dosed at 1:1 ratios and
applied to diesel engines above 3.0 MW with an exhaust stream of 500-
600 ppm NOX.
    (7) The effect on overall locomotive weight and balance when
applying DPF and SCR devices with a weight in excess of 8000 lbs and
volume in excess of 40 cubic feet mounted above the engine.
    (8) The expected effect on locomotive operating range when adding
urea storage equal to 5% of locomotive fuel capacity and a 2% decrease
in locomotive fuel efficiency.
    (9) Incidental emissions generation resulting from the production
and distribution of urea for railroad usage (200,000,000 gallons/year).
    (10) The comparative performance of a given engine on the marine v.
locomotive duty cycle to include an assessment of SCR technologies
(i.e., Zeolilte v. Vanadium), expected effectiveness for each
application, and any considerations that may be unique for one
application versus the other that could impact overall NOX
conversion effectiveness.
    (11) The impact of the proposed Tier 4 NOX limit of 1.3
g/hp-hr versus incrementally higher limits on fuel burn and greenhouse
gas emissions.
    EPA notes that many of these issues are addressed elsewhere in the
preamble and in the draft RIA. We invite comment on these questions in
the context of the information provided elsewhere on these issues. In
providing comments to these eleven questions, we ask that commenters
provide information both directly responsive to the individual question
and further to the relevance of the question in determining the
appropriate emission standard for diesel locomotives. For example,
question 1 lists a wide range of conditions for catalyst systems on a
diesel locomotive. In that context, EPA also invites comment on the
following questions.
     How do the shock loading, vibration loading, soot
exposure, and temperature exposure conditions listed in Question 1
compare to conditions faced by other applications of Zeolite-type urea
SCR systems that are either under development or that have been
developed for on-highway diesel, nonroad diesel, marine and stationary
gas turbine applications?
     Question 1 asserts that a locomotive catalyst design would
directly expose catalyst substrates to rain water, icing, water spray
and condensed frozen or liquid water during 20% of its life. Are there
catalyst packaging and installation issues that would necessitate any
direct exposure of catalyst substrates to weather?
     Question 1 implies that a locomotive catalyst design would
directly expose catalyst substrates to salt fogs consisting of 5 < plus-
minus> 1% salt concentration by weight with fallout rate between
0.00625 and 0.0375 ml/cm\2\/hr. What salt concentrations in salt fogs
and what fallout rates have SCR systems applied to ocean-going vessels
been exposed to? How would the systems designs, exposures and impacts
be similar to or different from locomotive applications? Are there
unique characteristics of locomotive catalyst installations that would
increase their exposure to salt fog relative to other applications
operated near or in ocean environments? What direct experiences have
ocean-going vessels had regarding the durability of their catalytic
emission control systems?
     Question 1 implies that locomotive catalyst systems must
withstand exposure to sand ingested by the engine at a rate of up to 50
pounds per hour at notch 8. The question also implies that locomotive
catalyst substrates must withstand exposure to a combination of red
china clay and silicon flour at a rate of up to one-quarter ton per
hour at notch 8. Are these appropriate metrics that reasonably take
into consideration the design of the locomotive air-intake and
filtration system and the ability of the engine and turbocharger
systems to withstand such extreme exposure to ingestion of abrasive
materials? Are tests replicating this condition routinely

conducted to demonstrate the durability of the engine and turbocharger
systems and emissions compliance following such high rates of engine
ingestion of abrasive materials?
     Questions 2 and 3 imply that greater than 45% DOC
oxidation efficiency is required to maintain Zeolite SCR catalyst
efficiency at greater than 94% NOX efficiency, and that 94%
NOX efficiency is required to meet the proposed Tier 4
NOX standard. Is greater than 45% oxidation efficiency for
an upstream DOC necessary for locomotives to meet the 1.3 g/bhp-hr
NOX standard over the range of exhaust temperature
encountered by locomotives over the line-haul duty cycle when using a
Zeolite-based SCR system? Is 94% NOX efficiency from the
current Tier 2 locomotive baseline even necessary to achieve 1.3 g/bhp-
hr NOX emissions when using a Zeolite SCR catalyst system
over the line-haul duty-cycle?
     What level of ammonia slip is achievable from modern urea-
SCR systems using closed-loop feedback control? Is 5 ppm an appropriate
level to set for maximum ammonia slip under any conditions?
     Is 5% of point the limit of zirconia-NOX sensor
accuracy? Does NOX sensor accuracy currently limit
NOX conversion efficiency of feedback controlled SCR
systems, and if so by how much? What level of NOX conversion
efficiency using a Zeolite-based SCR when not kinetically limited is
achievable using current feedback control systems using of zirconia-
NOX sensors? What level of NOX conversion
efficiency can be expected taking into consideration projected
NOX sensor and feedback control system development over the
next ten to fifteen years?
    Comments submitted should provide detailed technical information
and data to the extent possible. The EPA solicits comment on the extent
to which any factor may impact the ability to achieve the proposed
standard and if the proposed standard cannot be achieved in the
commenter's view, what standard can be achieved.

E. What Are EPA's Plans for Diesel Marine Engines on Large Ocean-Going
Vessels?

    Today's proposal covers marine diesel engines up to 30 l/cyl
displacement installed on vessels flagged or registered in the U.S.
There are two additional significant sources of air pollution from
diesel marine engines which are not covered by today's proposal: first,
marine diesel engines of any size (Category 1, 2 or 3) installed on
foreign-flagged vessels; and second, marine diesel engines at or above
30 l/cyl displacement (Category 3) installed on U.S. flagged vessels.
The largest environmental concern for these types of engines are the
large, ocean-going marine vessels (OGV), which are typically larger
than 2,000 gross tons and involved primarily in international commerce.
Ocean-going marine vessels typically are powered by one or more
Category 3 diesel engines for propulsion of the vessel, and they
typically also have several Category 2 engines to provide auxiliary
power. Engines on OGV are predominately fueled by residual fuel (often
called ``heavy fuel oil''), which is a by-product of distilling crude
oil to produce lighter petroleum products such as gasoline, distillate
diesel fuel, and kerosene and has a high sulfur content, up to 45,000
ppm.\120\ Ocean-going vessels are a significant contributor to air
pollution in the United States, in particular in coastal areas and
ports. Current projections indicate that on a national level, OGVs
flagged in the U.S. and other countries will contribute about 21
percent of mobile source PM, 12 percent NOX and 76 percent
of SOX in the year 2030. These contributions can be much
higher in some coastal and port areas. However, recent inventory
estimates performed for the California Air Resources Board and the
Commission for Environmental Cooperation in North America suggest that
we are significantly underestimating the emissions for C3 engines, by
as much as a factor of 2 or 3.\121\
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    \120\ Residual fuel also possesses a high viscosity and density,
which makes it harder to handle and use of this fuel requires
special equipment such as heaters, centrifuges, and purifiers. It
typically also has a high ash, and nitrogen content compared to
distillate diesel fuels. It is not produced to a set of narrow
specifications, and so fuel parameters can be highly variable.
    \121\ Corbett, J.J., et al. Estimation, Validation, and
Forecasts of Regional Commercial Marine Vessel Inventories, Tasks 1
and 2: Baseline Inventory and Ports Comparison, Final Report, dated
3 May 2006. Prepared for the California Air Resources Board, the
Californian Environmental Protection Agency and the Commission for
Environmental Cooperation in North America. ARB contract 04-346, CEC
Contract 113.11. A copy of this document can be found
athttp://www.arb.ca.gov/research/seca/jctask12.pdf.

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    EPA has a number of activities underway which hold promise for
reducing air pollution from OGVs. These include: a future rulemaking
action on C3 engine standards; negotiations underway at the
International Maritime Organization to establish a new set of
environmentally protective international emission standards for OGVs;
studies to assess the feasibility of establishing one or more
SOX Emission Control Areas adjacent to North America to
reduce SOX and particulate matter from OGVs; and voluntary
actions through our Clean Ports USA program.
(1) Future C3 Marine Rule
    In 2003 we issued a final rule for new C3 engines installed on U.S.
flagged vessels. That final action established NOX limits
for new C3 engines which are equal to the current international
NOX standards for C3 engines established through Annex VI of
the International Convention for the Prevention of Pollution from Ships
(MARPOL 73/78). The MARPOL standards are based on the capabilities of
emission control technologies from the early 1990s, and are
significantly higher then emission standards for any other mobile
source in the United States. In the 2003 final rule, we identified the
technical challenges associated with the application of after-treatment
technologies to these engines and vessels, but committed to revisiting
the issue of the appropriate long-term emission standards for C3 marine
engines, both those which are on vessels flagged in the U.S. and those
which are installed on foreign flagged vessels. In revisiting the
standards we indicated that we would consider the state of technology
that may permit deeper emission reductions and the status of
international action for more stringent standards. We committed to a
final Agency action by April 27, 2007.
    In 2003, we believed the next round of emission standard
discussions at the IMO would be well underway, if not concluded, by
April of 2006. In 2003, we also believed the IMO deliberations would be
one of the avenues to explore improvements in emission control
technology for C3 engines and ocean-going vessels, and would provide
valuable technical input for EPA's C3 rulemaking.
    Despite efforts by the United States Government at IMO,
deliberations regarding future emission standards for OGV did not begin
until April 2006. The current round of negotiations at IMO is expected
to continue through 2007. The discussions thus far at IMO have yielded
new technical information which EPA will be able to make use of in our
future C3 rulemaking. We expect to issue a revised schedule for the C3
rule in the next few months as well as solicit comments on the
appropriate technologies, standards, and lead time EPA should consider
for C3 standards.
(2) International Standards Deliberation at IMO
    With respect to the discussions currently underway at the IMO, the
United States Government is actively

engaged in the negotiation of a new set of international standards for
Annex VI to the International Convention for the Prevention of
Pollution from Ships (MARPOL Annex VI). Since the current Annex VI
NOX limits have entered into effect, and in the time frame
since EPA issued our 2003 rule, improvements in both in-cylinder and
external emission control technologies have been demonstrated, both in
the laboratory and on-board OGVs. These technologies offer the
potential to substantially reduce NOX emissions from OGVs.
In addition, the use of lower sulfur residual or distillate fuels and/
or the use of SOX scrubbing technologies offer the potential
to substantially reduce PM and SOX emissions from OGVs. We
believe the member states of the IMO, including the United States, have
a unique opportunity to establish appropriate long-term standards to
address air pollution from OGVs.
    The current discussions for the next tier of engine emission
standards at IMO also provide an opportunity to apply emission
reduction technologies to existing vessels. EPA is a strong supporter
of reducing pollution of existing vessels through mandatory rebuild/
retrofit requirements and we will continue to pursue this objective at
the IMO.
(3) SOX Emission Control Areas
    The existing international agreements adopted by the IMO provide
the opportunity for signatories to Annex VI of the International
Convention for the Prevention of Pollution from Ships to propose the
designation of one or more SOX Emission Control Areas
(SECA). When operating in a SECA, all OGVs must either use fuel with a
maximum sulfur content of 15,000 ppm or use emission control technology
such that the vessel meets a SOX limit of 6 g/kW-hr (a value
deemed equivalent to 15,000 ppm sulfur). This represents only
approximately a 45 percent reduction in SOX emissions
compared to the world-wide fuel sulfur average for heavy-fuel oil of
about 27,000 ppm. EPA is currently performing environmental impact and
economic analyses that will assist the federal government in making a
determination whether the U.S. Government should consider a proposal
designating a SECA to one or more areas adjacent to North America. We
are working closely with the Canadian Government Canada) on these
efforts, and we also intend to coordinate our actions with Mexico. This
could allow for the inclusion of additional coastal areas within SECAs
for North American. It must be noted that the United States has not yet
ratified Annex VI and any decision regarding whether the United States
will pursue the designation of a SECA will be influenced by where the
United States stands with respect to ratification of MARPOL Annex VI.
(4) Clean Ports USA
    As part of EPA's National Clean Diesel Campaign, Clean Ports USA is
an incentive-based, public-private partnership designed to reduce
emissions from existing diesel engines and vessels at ports. The Clean
Ports USA team works to bring together partners and build coalitions to
identify and develop cost-effective diesel emission reduction projects
that address the key issues affecting ports today. EPA provides
technical support in verifying the effectiveness of retrofit
technology, to ensure through rigorous testing that the emissions
reductions promised by vendors are in fact achieved in the field.
    Clean Ports USA is providing incentives to port authorities,
terminal operators, cargo interests, trucking fleets, and maritime
fleet owners to:
     Retrofit and replace older diesel engines with verified
technologies such as diesel oxidation catalysts (DOCs), diesel
particulate filters (DPFs).
     Use cleaner fuels (ultra-low sulfur diesel fuel,
emulsions).
     Increase operational efficiency, including environmental
management systems, logistics, and appointment systems.
     Reduce engine idling.
     Replace older engines with new, cleaner engines.
    Additional information is available on the Clean Ports USA Web site
at http://www.epa.gov/cleandiesel/ports.

IV. Certification and Compliance Program

    This section describes the regulatory changes proposed for the
locomotive and marine compliance programs. The most obvious change is
that the proposed regulations have been written in plain language. They
are structured to contain the provisions that are specific to
locomotives in a new proposed part 1033 and contain the provisions that
are specific to marine engines and vessels in a new proposed part 1042.
We also propose to apply the general provisions of existing parts 1065
and 1068.\122\ The proposed plain language regulations, however, are
not intended to significantly change the compliance program, except as
specifically noted in today's notice (and we are not reopening for
comment the substance of any part of the program that remains unchanged
substantively). As proposed, these plain language regulations would
supersede the regulations in part 92 and 94 (for Categories 1 and 2) as
early as the 2008 model year. See section III for the starting dates
for different engines. The changes from the existing programs are
described below along with other notable aspects of the compliance
program. Note: The term manufacturer is used in this section to include
locomotive and marine manufacturers and locomotive remanufacturers. It
would also include marine remanufacturers if we finalize remanufacture
standards.
---------------------------------------------------------------------------

    \122\ In a separate rulemaking, which has been submitted to the
Office of Management and Budget (OMB) for review, we will be
proposing modifications to the existing provisions of 40 CFR part
1068. We have placed into the docket for this current proposal, a
copy of the draft part 1068 regulatory language that was submitted
to OMB. Readers interested in the compliance provisions that would
apply to locomotives and marine diesel engines should also read the
actual regulatory changes that will be proposed in that upcoming
rulemaking.
---------------------------------------------------------------------------

A. Issues Common to Locomotives and Marine

    For many aspects of compliance, we are proposing similar provisions
for marine engines and locomotives, which are discussed in this
section. Also included in this section are issues which are similar,
but where we are proposing different provisions. The other compliance
issues are discussed in sections IV. B. (for locomotives) and IV. C.
(for marine).
(1) Modified Test Procedures
(a) Incorporation of Part 1065 Test Procedures for Locomotive and
Marine Diesel Engines
    As part of our initiative to update the content, organization and
writing style of our regulations, we are revising our test procedures.
We have grouped all of our engine dynamometer and field testing test
procedures into one part entitled, ``Part 1065: Test Procedures.'' For
each engine or vehicle sector for which we have recently promulgated
standards (such as land-based nonroad diesel engines or recreational
vehicles), we identified an individual part as the standard-setting
part for that sector. These standard-setting parts then refer to one
common set of test procedures in part 1065. We intend in this proposal
to continue this process of having all our engine programs refer to a
common set of procedures by applying part 1065 to all locomotive and
marine diesel engines.
    In the past, each engine or vehicle sector had its own set of
testing procedures. There are many similarities in test procedures
across the various sectors. However, as we introduced new regulations
for individual sectors, the

[[Continued on page 15987]]

]

[[pp. 15987-16036]] Control of Emissions of Air Pollution From Locomotive Engines and
Marine Compression-Ignition Engines Less Than 30 Liters per Cylinder

[[Continued from page 15986]]

more recent regulations featured test procedure updates and
improvements that the other sectors did not have. As this process
continued, we recognized that a single set of test procedures would
allow for improvements to occur simultaneously across engine and
vehicle sectors. A single set of test procedures is easier to
understand than trying to understand many different sets of procedures,
and it is easier to move toward international test procedure
harmonization if we only have one set of test procedures. We note that
procedures that are particular for different types of engines or
vehicles, for example, test schedules designed to reflect the
conditions expected in use for particular types of vehicles or engines,
would remain separate and would be reflected in the standard-setting
parts of the regulations.
    As compared to the existing locomotive and marine diesel test
procedures found in parts 92 and 94, part 1065 test procedures are
organized and written for improved clarity. In addition, we are
proposing part 1065 for locomotive and marine diesel engines to improve
the content of their respective testing specifications, including the
following:
     Specifications and calculations written in the
international system of units (SI).
     Procedures by which manufacturers can demonstrate that
alternate test procedures are equivalent to specified procedures.
     Specifications for new measurement technology that has
been shown to be equivalent or more accurate than existing technology.
     Procedures that improve test repeatability.
     Calculations that simplify emissions determination.
     New procedures for field testing engines.
     More comprehensive sets of definitions, references, and
symbols.
     Calibration and accuracy specifications that are scaled to
the applicable standard, which allows us to adopt a single
specification that applies to a wide range of engine sizes and
applications.
    Some emission-control programs already rely on the test procedures
in part 1065. These programs regulate land-based on-highway heavy-duty
engines, land-based nonroad diesel engines, recreational vehicles, and
nonroad spark-ignition engines over 19 kW.
    We are adopting the lab-testing and field-testing specifications in
part 1065 for all locomotive and marine diesel engines. These
procedures replace those currently published in parts 92 and 94. We are
making a gradual transition from the part 92 and 94 procedures. For
several years, manufacturers would be able to optionally use the part
1065 procedures. Part 1065 procedures would be required for any new
testing by the model year in which the Tier 4 standard applies to a
locomotive or marine diesel engine or by 2012 for a locomotive or
marine diesel engine that is not proposed to be subject to a Tier 4
standard. For any testing completed for any emissions standard that is
less stringent than the respective Tier 4 standard, manufacturers may
continue to rely on carryover test data based on part 92 or 94
procedures to certify engine families in later years. In addition, for
any other programs that refer to the test procedures in parts 92 or 94,
we are including updated references for all these other programs to
refer instead to the appropriate cite in part 1065.
    Part 1065 is also advantageous for in-use testing because it
specifies the same procedures for all common parts of field testing and
laboratory testing. It also contains new provisions that help ensure
that engines are tested in a laboratory in a way that is consistent
with how they operate in use. These new provisions would ensure that
engine dynamometer lab testing and field testing are conducted in a
consistent way.
    In the future, we may apply the test procedures specified in part
1065 to other types of engines, so we encourage companies involved in
producing or testing other engines to stay informed of developments
related to these test procedures.
(b) Revisions to Part 1065
    Part 1065 was originally adopted on November 8, 2002 (67 FR 68242),
and was initially applicable to standards regulating large nonroad
spark-ignition engines and recreational vehicles under 40 CFR parts
1048 and 1051. The recent rulemaking adopting emission standards for
nonroad diesel engines has also made part 1065 optional for Tier 2 and
Tier 3 nonroad standards and required for Tier 4 standards. The test
procedures initially adopted in part 1065 were sufficient to conduct
testing, but on July 13, 2005 (70 FR 11534) we promulgated a final rule
that reorganized these procedures and added content to make various
improvements. In particular, we reorganized part 1065 by subparts as
shown below:
     Subpart A: General provisions; global information on
applicability, alternate procedures, units of measure, etc.
     Subpart B: Equipment specifications; required hardware for
testing.
     Subpart C: Measurement instruments.
     Subpart D: Calibration and verifications; for measurement
systems.
     Subpart E: Engine selection, preparation, and maintenance.
     Subpart F: Test protocols; step-by-step sequences for
laboratory testing and test validation.
     Subpart G: Calculations and required information.
     Subpart H: Fuels, fluids, and analytical gases.
     Subpart I: Oxygenated fuels; special test procedures.
     Subpart J: Field testing and portable emissions
measurement systems.
     Subpart K: Definitions, references, and symbols.
    The regulations now prescribe scaled specifications for test
equipment and measurement instruments by parameters such as engine
power, engine speed and the emission standards to which an engine must
comply. That way this single set of specifications would cover the full
range of engine sizes and our full range of emission standards.
Manufacturers would be able to use these specifications to determine
what range of engines and emission standards may be tested using a
given laboratory or field testing system.
    The content of part 1065 is mostly a combination of content from
our most recent updates to other test procedures and from test
procedures specified by the International Organization for
Standardization (ISO). In some cases, however, there is new content
that never existed in previous regulations. This new content addresses
very recent issues such as measuring very low concentrations of
emissions, using new measurement technology, using portable emissions
measurement systems, and performing field testing. A detailed
description of the changes is provided in a memorandum to the
docket.\123\
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    \123\ Memorandum to docket EPA-HQ-OAR-2003-0190, ``Redline/
Strikeout of 40 CFR 1065 (Test Procedures) Changes and Additions''.
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    The new content also reflects a shift in our approach for
specifying measurement performance. In the past we specified numerous
calibration accuracies for individual measurement instruments, and we
specified some verifications for individual components, such as
NO2 to NO converters. We have shifted our focus away from
individual instruments and toward the overall performance of complete
measurement systems. We did this for several reasons. First, some of
what we specified in the

past precluded the implementation of new measurement technologies.
These new technologies, sometimes called ``smart analyzers'', combine
signals from multiple instruments to compensate for interferences that
were previously tolerable at higher emissions levels. These analyzers
are useful for detecting low concentrations of emissions. They are also
useful for detecting emissions from raw exhaust, which can contain high
concentrations of interferences, such as water vapor. This is
particularly important for field testing, which will most likely rely
upon raw exhaust measurements. Second, this new ``systems approach''
challenges complete measurement systems with a series of periodic
verifications, which we feel will provide a more robust assurance that
a measurement system as a whole is operating properly. Third, the
systems approach provides a direct pathway to demonstrate that a field
test system performs similarly to a laboratory system. This is
explained in more detail in item 10 below. Finally, we feel that our
systems approach will lead to a more efficient way of assuring
measurement performance in the laboratory and in the field. We believe
that this efficiency will stem from less frequent individual instrument
calibrations, and higher confidence that a complete measurement system
is operating properly.
    We have organized the new content relating to measurement systems
performance into subparts C and D. We specify measurement instruments
in subpart C and calibrations and periodic system verifications in
subpart D. These two subparts apply to both laboratory and field
testing. We have organized content specific to running a laboratory
emissions test in subpart F, and we separated content specific to field
testing in subpart J.
    In subpart C we specify the types of acceptable instruments, but we
only recommend individual instrument performance. We provide these
recommendations as guidance for procuring new instruments. We feel that
the periodic verifications that we require in subpart D will
sufficiently evaluate the individual instruments as part of their
respective overall measurement systems. In subpart F we specify
performance validations that must be conducted as part of every
laboratory test. In subpart J we specify similar performance
validations for field testing that must be conducted as part of every
field test. We feel that the periodic verifications in subpart D and
the validations for every test that we prescribed in subparts F and J
ensure that complete measurement systems are operating properly.
    In subpart J we also specify an additional overall verification of
portable emissions measurement systems (PEMS). This verification is a
comprehensive comparison of a PEMS versus a laboratory system, and it
may take several days of laboratory time to set up, run, and evaluate.
However, we only require that this particular verification must be
performed at least once for a given make, model, and configuration of a
field test system.
    Below is a brief description of the content of each subpart,
highlighting some of the most important content.
(i) Subpart A: General Provisions
    In Subpart A we identify the applicability of part 1065 and
describe how procedures other than those in part 1065 may be used to
comply with a standard-setting part. In Sec.  1065.10(c)(1), we specify
that testing must be conducted in a way that represents in-use engine
operation, such that in the rare case where provisions in part 1065
result in unrepresentative testing, other procedures would be used.
    Other information in this subpart includes a description of the
conventions we use regarding units and certain measurements; and we
discuss recordkeeping. We also provide an overview of how emissions and
other information are used to determine final emission results. The
regulations in Sec.  1065.15 include a figure illustrating the
different ways we allow brake-specific emissions to be calculated.
    In this same subpart, we describe how continuous and batch sampling
may be used to determine total emissions. We also describe the two ways
of determining total work that we approve. Note that the figure
indicates our default procedures and those procedures that require
additional approval before we will allow them.
(ii) Subpart B: Equipment Specifications
    Subpart B first describes engine and dynamometer related systems.
Many of these specifications are scaled to an engine's size, speed,
torque, exhaust flow rate, etc. We specify the use of in-use engine
subsystems such as air intake systems wherever possible in order to
best represent in-use operation when an engine is tested in a
laboratory.
    Subpart B also describes sampling dilution systems. These include
specifications for the allowable components, materials, pressures, and
temperatures. We describe how to sample crankcase emissions. Subpart B
also specifies environmental conditions for PM filter stabilization and
weighing.
    The regulations in Sec.  1065.101 include a diagram illustrating
all the available equipment for measuring emissions.
(iii) Subpart C: Measurement Instruments
    Subpart C specifies the requirements for the measurement
instruments used for testing. In subpart C we recommend accuracy,
repeatability, noise, and response time specifications for individual
measurement instruments, but note that we only require that overall
measurement systems meet the calibrations and verifications in Subpart
D.
    In some cases we allow instrument types to be used where we
previously did not allow them in parts 92 or 94. For example, we now
allow the use of a nonmethane cutter for NMHC measurement, a
nondispersive ultraviolet analyzer for NOX measurement, a
zirconia sensor for O2 measurement, various raw-exhaust flow
meters for laboratory and field testing measurement, and an ultrasonic
flow meter for CVS systems.
(iv) Subpart D: Calibrations and Verifications
    Subpart D describes what we mean when we specify accuracy,
repeatability and other parameters in Subpart C. We are adopting
calibrations and verifications that scale with engine size and with the
emission standards to which an engine is certified. We are replacing
some of what we have called ``calibrations'' in the past with a series
of verifications, such as a linearity verification, which essentially
verifies the calibration of an instrument without specifying how the
instrument must be initially calibrated. Because new instruments have
built-in routines that linearize signals and compensate for various
interferences, our existing calibration specifications in parts 92 and
94 sometimes conflicted with an instrument manufacturer's instructions.
In addition, there are new verifications in subpart D to ensure that
the new instruments we specify in Subpart C are used correctly.
(v) Subpart E: Engine Selection, Preparation, and Maintenance
    Subpart E describes how to select, prepare, and maintain a test
engine.
(vi) Subpart F: Test Protocols
    Subpart F describes the step-by-step protocols for engine mapping,
test cycle generation, test cycle validation, pre-test preconditioning,
engine starting, emission sampling, and post-test validations. We allow
modest corrections for drift of emission analyzer

signals within a certain range. We recommend a step-by-step procedure
for weighing PM samples.
(vii) Subpart G: Calculations and Required Information
    Subpart G includes all the calculations required in part 1065.
Subpart G includes definitions of statistical quantities such as mean,
standard deviation, slope, intercept, t-test, F-test, etc. By defining
these quantities mathematically we intend to resolve any potential mis-
communication when we discuss these quantities in other subparts. We
have written all calculations for calibrations and emission
calculations in international units. For our standards that are not
completely in international units (i.e., grams/horsepower-hour, grams/
mile), we specify in part 1065 the correct use of internationally
recognized conversion factors.
    We also specify emission calculations based on molar quantities for
flow rates, instead of volume or mass. This change eliminates the
frequent confusion caused by using different reference points for
standard pressure and standard temperature. Instead of declaring
standard densities at standard pressure and standard temperature to
convert volumetric concentration measurements to mass-based units, we
declare molar masses for individual elements and compounds. Since these
values are independent of all other parameters, they are known to be
universally constant.
(viii) Subpart H: Fuels, Fluids, and Analytical Gases
    Subpart H specifies test fuels, lubricating oils and coolants, and
analytical gases for testing. We eliminated the Cetane Index
specification for all diesel fuels, because the existing specification
for Cetane Number sufficiently determines the cetane levels of diesel
test fuels. We do not identify any detailed specification for service
accumulation fuel. Instead, we specify that service accumulation fuel
may be either a test fuel or a commercially available in-use fuel. We
include a list of ASTM specifications for in-use fuels as examples of
appropriate service accumulation fuels. We include an allowance for
engine manufacturers to use in-use test fuels that do not meet all of
the specifications, provided that the in-use fuel does not adversely
affect the manufacturer's ability to demonstrate compliance with the
applicable standard. For example a fuel that would result in lower
emissions versus the certification fuel would generally adversely
affect a manufacturers ability to demonstrate compliance with the
applicable standards. We also allow the use of ASTM test methods
specified in 40 CFR Part 80 in lieu of those specified in part 1065. We
did this because we more frequently review and update the ASTM methods
in 40 CFR Part 80 versus those in part 1065.
(ix) Subpart I: Oxygenated Fuels
    Subpart I describes special procedures for measuring certain
hydrocarbons whenever oxygenated fuels are used. We allow the use of
the California NMOG test procedures to measure alcohols and carbonyls.
(x) Subpart J: Field Testing and Portable Emissions Measurement Systems
    As described in Subpart J, Portable Emissions Measurement Systems
(PEMS) must generally meet the same specifications and verifications
that laboratory instruments must meet, according to subparts B, C, and
D. However, we allow some deviations from laboratory specifications. In
addition to meeting many of the laboratory system requirements, a PEMS
must meet an overall verification relative to a series of laboratory
measurements. This verification involves repeating a duty cycle several
times. This is a comprehensive verification of a PEMS. We are also
adopting a procedure for preparing and conducting a field test, and we
are adopting drift corrections for PEMS emission analyzers. Given the
evolving state of PEMS technology, the field-testing procedures provide
for a number of known measurement techniques. We have added provisions
and conditions for the use of PEMS in an engine dynamometer laboratory
to conduct laboratory testing.
(xi) Subpart K: Definitions, References, and Symbols
    In Subpart K we define terms frequently used in part 1065. For
example we have defined ``brake power'', ``constant-speed engine'', and
``aftertreatment'' to provide more clarity, and we have definitions for
things such as ``300 series stainless steel'', ``barometric pressure'',
and ``operator demand''. There are definitions such as ``duty cycle''
and ``test interval'' to distinguish the difference between a single
interval over which brake-specific emissions are calculated and the
complete cycle over which emissions are evaluated in a laboratory. We
also present a thorough and consistent set of symbols, abbreviations,
and acronyms in subpart K.
(2) Certification Fuel
    It is well-established that measured emissions may be affected by
the properties of the fuel used during the test. For this reason, we
have historically specified allowable ranges for test fuel properties
such as cetane and sulfur content. These specifications are intended to
represent most typical fuels that are commercially available in use.
This helps to ensure that the emissions reductions expected from the
standards occur in use as well as during emissions testing. Because we
have reduced the upper limit for locomotive and marine diesel fuel
sulfur content for refiners to 15 ppm in 2012, we are proposing to
establish new ranges of allowable sulfur content for diesel test fuels.
See sectionC.(5) for information about testing marine engines designed
to use residual fuel.
    For marine diesel engines, we are proposing the use of ULSD fuel as
the test fuel for Tier 3 and later standards (when the new plain
language regulations begin to apply). We believe this would correspond
to the fuels that these engines will see in use over the long term. We
recognize that this approach would mean that some marine engines would
use a test fuel that is lower in sulfur than in-use fuel during the
first few years, and that other Tier 2 marine engines would use a test
fuel that is higher in sulfur than fuel already available in use when
they are produced. However, we believe that it is more important to
align changes in marine test fuels with changes in the PM standards
than strictly with changes in the in-use fuel. Nevertheless, we are
proposing to allow certification with fuel meeting the 7 to 15 ppm
sulfur specification for Tier 2 to simplify testing, but would require
PM emissions to be corrected to be equivalent to testing conducted with
the specified fuel.
    For locomotives, we are proposing to require that Tier 4 engines be
certified based on ULSD test fuels. We are also proposing to require
that these locomotives use ULSD in the field. We would continue to
allow older locomotives to use in the field low sulfur diesel (LSD)
fuel, which is the intermediate grade of fuel with sulfur levels
between 15 and 500 ppm. Thus, we are proposing to require that
remanufacture systems for most of these locomotives be certified on LSD
test fuel. We are proposing to allow the use of test fuels other than
those specified here. Specifically, we would allow the use of ULSD
during emission testing for locomotives otherwise required to use LSD,
provided they do not use sulfur-

sensitive technology (such as oxidation catalysts). However, as a
condition of this allowance, the manufacturer would be required to add
an additional amount to the measured PM emissions to make them
equivalent to what would have been measured using LSD. For example, we
would allow a manufacturer to test with ULSD if they adjusted the
measured PM emissions upward by 0.01 g/bhp-hr (which would be a
relatively conservative adjustment).
    We are proposing special fuel provisions for Tier 3 locomotives and
Tier 2 remanufacture systems. We are proposing that the test fuel for
these be ULSD without sulfur correction since these locomotives will
use ULSD in use for most of their service lives. However, unlike Tier 4
locomotives, we would not require them to be labeled to require the use
of ULSD, unless they included sulfur sensitive technology.
    We are proposing a new flexibility for locomotives and Category 2
marine engines to reduce fuel costs for testing. Because these engines
can consume 200 gallons of diesel fuel per hour at full load, fuel can
represent a significant fraction of the testing cost, especially if the
manufacturer must use specially blended fuel rather than commercially
available fuel. To reduce this cost, we are proposing to allow
manufacturers to perform testing of locomotives and Category 2 engines
with commercially available diesel fuel.
    For both locomotive and marine engines, all of the specifications
described above would apply to emission testing conducted for
certification, selective enforcement audits, and in-use, as well as any
other testing for compliance purposes for engines in the designated
model years. Any compliance testing of previous model year engines
would be done with the fuels designated in our regulations for those
model years.
(3) Supplemental Emission Standards
    We are proposing to continue the supplemental emission standards
for locomotives and marine engines. For locomotives, this means we
would continue to apply notch emission caps, based on the emission
rates in each notch, as measured during certification testing. We
recognize that for our Tier 4 proposed standards it would not be
practical to measure very low levels of PM emissions separately for
each notch during testing, and thus we are proposing a change in the
calculation of the PM notch cap for Tier 4 locomotives. All other notch
caps would be determined and applied as they currently are under 40 CFR
92.8(c). See Sec.  1033.101(e) of the proposed regulations for the
detailed calculation.
    Marine engines would continue to be subject to not-to-exceed (NTE)
standards, however, we are proposing certain changes to these standards
based upon our understanding of in-use marine engine operation and
based upon the underlying Tier 3 and Tier 4 duty cycle emissions
standards that we are proposing. As background, we determine NTE
compliance by first applying a multiplier to the duty-cycle emission
standard, and then we compare to that value an emissions result that is
recorded when an engine runs within a certain range of engine
operation. This range of operation is called an NTE zone (see 40 CFR
94.106). The first regulation of ours that included NTE standards was
the commercial marine diesel regulation, finalized in 1999. After we
finalized that regulation, we promulgated other NTE regulations for
both heavy-duty on-highway and nonroad diesel engines. We also
finalized a regulation that requires heavy-duty on-highway engine
manufacturers to conduct field testing to demonstrate in-use compliance
with the on-highway NTE standards. Throughout our development of these
other regulations, we have learned many details about how best to
specify NTE zones and multipliers that would ensure the greatest degree
of in-use emissions control, while at the same time would avoid
disproportionately stringent requirements for engine operation that has
only a minor contribution to an engine's overall impact on the
environment. Based upon the Tier 3 and Tier 4 standards we are
proposing--and our best information of in-use marine engine operation--
we are proposing certain improvements to our marine NTE standards.
    For marine engines we are proposing a broadening of the NTE zones
in order to better control emissions in regions of engine operation
where an engine's emissions rates (i.e. grams/hour, tons/day) are
greatest; namely at high engine speed and high engine load. This is
especially important for commercial marine engines because they
typically operate at steady-state at high-speed and high-load
operation. This proposed change also would make our marine NTE zones
much more similar to our on-highway and nonroad NTE zones.
Additionally, we analyzed different ways to define the marine NTE
zones, and we determined a number of ways to improve and simplify the
way we define and calculate the borders of these zones. We feel that
these improvements would help clarify when an engine is operating
within a marine NTE zone. Please refer to section 1042.101(c) of our
draft proposed regulations for a description of our proposed NTE
standards. Note that we currently specify different duty cycles to
which a marine engine may be certified, based upon the engine's
specific application (e.g., fixed-pitch propeller, controllable-pitch
propeller, constant speed, etc.). Correspondingly, we also have a
unique NTE zone for each of these duty cycles. These different NTE
zones are intended to best reflect an engine's real-world range of
operation for that particular application. Because we are proposing
changes to the shapes of these NTE zones, we request comment as to
whether or not these changes best reflect actual in-use operation of
marine engines.
    We are also proposing changes to the NTE multipliers. We have
analyzed how our proposed Tier 3 and Tier 4 emissions standards would
affect the stringency of our current marine NTE standards, especially
in comparison to the stringency of the underlying duty cycle standards.
We recognized that in certain sub-regions of our proposed NTE zones,
slightly higher multipliers would be necessary because of the way that
our more stringent proposed Tier 3 and Tier 4 emissions standards would
affect the stringency of the NTE standards. For comparison, our current
marine NTE standards contain multipliers that range in magnitude from
1.2 to 1.5 times the corresponding duty cycle standard. In the changes
we are proposing, the new multipliers would range from 1.2 to 1.9 times
the standard. Even with these slightly higher NTE multipliers, we are
confident that our proposed changes to the marine NTE standards would
ensure the greatest degree of in-use emissions control. We are also
confident that our proposed changes to the marine NTE standards would
continue to ensure proportional emissions reductions, across the full
range of marine engine operation. Because we are proposing changes to
the NTE multipliers, we request comment as to whether or not these
changes best reflect actual in-use emissions profiles of marine engines
throughout the NTE zones we are proposing.
    We are also proposing to adopt other NTE provisions for marine
engines that are similar to our existing heavy-duty on-highway and
nonroad diesel NTE standards. We are proposing these particular changes
to account for the implementation of catalytic exhaust treatment
devices on marine engines and to account for when a marine engine
rarely operates within a limited region of the NTE zone (i.e. less than
5 percent of in-use operation). We feel that these provisions have been
effective

in our on-highway and nonroad NTE programs; therefore, we are proposing
to adopt them for our marine NTE standards as well.
    We are also proposing for the first time auxiliary marine engine
NTE standards, effective for both Tier 3 and Tier 4 auxiliary marine
engines. Since these engines are similar to nonroad constant speed
engines, we propose to adopt the same NTE standards for auxiliary
marine engines as we have already finalized for nonroad constant speed
engines. Specifically, these engines are engines certified to the ISO
8178-1 D2 test cycle, illustrated in 40 CFR Sec.  94.105, Table B-4.
Refer to 40CFR Sec.  1039.101(e) for our constant speed nonroad engine
NTE standards. Because we are proposing marine diesel Tier 3
implementation dates in the 2012 timeframe, we request comment as to
whether or not additional lead-time might be necessary to marinize and
certify NTE-compliant nonroad engines to the marine diesel Tier 3
standards, especially since it will be within that same timeframe that
the similar nonroad Tier 4 engines will be NTE-certified for nonroad
use.
    We request comment regarding the changes we are proposing for the
marine NTE standards.
(4) Emission Control Diagnostics
    As described below, we are requesting comment on (but not
proposing) a requirement that all Tier 4 engines include simple engine
diagnostic system to alert operators to general emission-related
malfunctions. (See section IV.A.(7) for related requirements involving
SCR systems.) We are, however, proposing special provisions for
locomotives that include emission related diagnostics. First, we would
require locomotive operators to respond to malfunction indicators by
performing the required maintenance or inspection. Second, locomotive
manufacturers would be allowed to repair such malfunctioning
locomotives during in-use compliance testing (they would still be
required to include a description of the malfunction in the in-use
testing report.). This approach would take advantage of the unique
market structure with two major manufacturers and only a few railroads
buying nearly all of the freshly manufactured locomotives. The proposed
provisions would create incentives for both the manufacturers and
railroads to work together to develop a diagnostic system that
effectively revealed real emission malfunctions. Our current
regulations already require that locomotive operators complete all
manufacturer-specified emission-related maintenance and this new
requirement would treat repairs indicated by diagnostic systems as such
emission-related maintenance. Thus, the railroads would have a strong
incentive to make sure that they only had to perform this additional
maintenance when real malfunctions were occurring. On the other hand,
manufacturers would want to have all emission malfunctions revealed so
that when they test an in-use locomotive they could repair identified
malfunction before testing if the railroad had not yet done it.
    At this time, we are requesting comment on a adopting a detailed
regulatory program to require that all Tier 4 locomotives and marine
engines include a specific engine diagnostic system. We believe that
most of these engines will be equipped with a basic diagnostic system
for other purposes, so codifying a uniform convention based largely on
these preexisting systems could be appropriate. Manufacturers would
generally not be required to monitor actual emission levels, but rather
would be required to monitor functionality. Such systems could be very
helpful in maintaining emission performance during the useful life and
ensuring that malfunctioning marine catalysts would be replaced.
However, we also believe that it might be more appropriate to address
this issue in a future rulemaking in the broader context of all nonroad
diesel engines.
(5) Monitoring and Reporting of Emissions Related Defects
    We are proposing to apply the defect reporting requirements of
Sec.  1068.501 to replace the provisions of subparts E in parts 92 and
94. This would result in two significant changes for manufacturers.
First, Sec.  1068.501 obligates manufacturers to tell us when they
learn that emission control systems are defective and to conduct
investigations under certain circumstances to determine if an emission-
related defect is present. Manufacturers must initiate these
investigations when warranty information, parts shipments, and any
other information which is available and indicates that a defect
investigation may be fruitful. For this purpose, we consider defective
any part or system that does not function as originally designed for
the regulatory useful life of the engine or the scheduled replacement
interval specified in the manufacturer's maintenance instructions. The
parts and systems are those covered by the emissions warranty, and
listed in Appendix I and II of part 1068. As we noted in previous
rulemakings, we believe the investigation requirement is necessary
because it will allow both EPA and the engine manufacturers to fully
understand the significance of any unusually high rates of warranty
claims and parts replacements for parts or parameters that may have an
impact on emissions. We believe that as part of its normal product
quality practices, prudent engine manufacturers already conduct a
thorough investigation when available data indicate recurring parts
failures. Such data is valuable and readily available to most
manufacturers and, under this proposal it must be considered to
determine whether or not there is a possible defect of an emission-
related part.
    The second change is related to reporting thresholds. Defect
reports submitted in compliance with the current regulations are based
on a single threshold applicable to engine families of all production
volumes. The single threshold in the existing regulations rarely
results in reporting of defects in the smallest engine families covered
by this regulation because a relatively high proportion of such engines
would have to be known to be defective before reporting is required
under a fixed threshold scheme. Therefore, under Sec.  1068.501, the
threshold for reporting for the smallest engine families would
generally be decreased as compared to the current requirements. These
thresholds were established during our rulemaking adopting Tier 4
standards for nonroad diesel engines.\124\ Those engines are
substantially similar to the engines used in the marine and locomotive
sectors, and thus, we believe that these thresholds will also be
appropriate for these engines.
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    \124\ 69 FR 38957, June 29, 2004.
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    We are aware that accumulation of warranty claims and part
shipments will likely include many claims and parts that do not
represent defects, so we are establishing a relatively high threshold
for triggering the manufacturer's responsibility to investigate whether
there is, in fact, a real occurrence of an emission-related defect.
Manufacturers are not required to count towards the investigation
threshold any replacement parts they require to be replaced at
specified intervals during the useful life, as specified in the
application for certification and maintenance instructions to the
owner, because shipments of such parts clearly do not represent
defects. All such parts would be excluded from investigation of
potential defects and reporting of defects, whether or not any specific
part was, in fact, shipped for specified replacement. This proposal is
intended to require manufacturers to use

information we would expect them to keep in the normal course of
business. We believe in most cases manufacturers would not be required
to institute new programs or activities to monitor product quality or
performance. A manufacturer that does not keep warranty or replacement
part information may ask for our approval to use an alternate defect-
reporting methodology that is at least as effective in identifying and
tracking potential emissions related defects as the proposed
requirements. However, until we approve such a request, the proposed
thresholds and procedures continue to apply.
    The thresholds for investigation are generally ten percent of total
production to date with special limits for small volume engine
families. Please note, manufacturers would not investigate for emission
related defects until either warranty claims or parts shipments
separately reach the investigation threshold. We recognize that a part
shipment may ultimately be associated with a particular warranty claim
in the manufacturer's database and, therefore, warranty claims and
parts shipments would not be aggregated for the purpose of triggering
the investigation threshold under this proposal.
    The second threshold in this proposal specifies when a manufacturer
must report that there is an emission-related defect. This threshold
involves a smaller number of engines because each potential defect
would have been screened to confirm that it is an emission-related
defect. In counting engines to compare with the defect-reporting
threshold, the manufacturer would consider a single engine family and
model year. However, when a defect report is required, the manufacturer
would report all occurrences of the same defect in all engine families
and all model years which use the same part. For engines subject to
this proposal, the threshold for reporting a defect is two percent of
total production for any single engine family with special limits for
small volume engine families. It is important to note that while we
regard occurrence of the defect threshold as proof of the existence of
a reportable defect, we do not regard that occurrence as conclusive
proof that recall or other action is merited.
    If the number of engines with a specific defect is found to be less
than the threshold for submitting a defect report, but information,
such as warranty claims or parts shipment data, later indicates
additional potentially defective engines, under this proposal the
information must be aggregated for the purpose of determining whether
the threshold for submitting a defect report has been met. If a
manufacturer has actual knowledge from any source that the threshold
for submitting a defect report has been met, a defect report would have
to be submitted even if the trigger for investigating has not yet been
met. For example, if manufacturers receive information from their
dealers, technical staff or other field personnel showing conclusively
that there is a recurring emission-related defect, they would have to
submit a defect report if the submission threshold is reached.
    For both the investigation and reporting thresholds, Sec.  1068.501
specifies lower thresholds for very large engines over 560 kW. A defect
in these engines can have a much greater impact than defects in smaller
engines due to their higher gram per hour emission rates and the
increased likelihood that such large engines will be used more
continuously.
(6) Rated Power
    We are proposing to specify how to determine maximum engine power
in the regulations for both locomotives and marine engines. The term
``maximum engine power'' would be used for marine engines instead of
previously undefined terms such as ``rated power'' or ``power rating''
to specify the applicability of the standards. We are not proposing to
define these terms for our purposes because they already have
commercial meanings. The addition of this definition is intended to
allow for more objective applicability of the standards. More
specifically, for marine engines, we are proposing that maximum engine
power would mean the maximum brake power output on the nominal power
curve for an engine.
    Currently, rated power and power rating are undefined and are
specified by the manufacturer during certification. This makes the
applicability of the standards unnecessarily subjective and confusing.
One manufacturer may choose to define rated power as the maximum
measured power output, while another may define it as the maximum
measured power at a specific engine speed. Using this second approach,
an engine's rated power may be somewhat less than the true maximum
power output of the engine. Given the importance of engine power in
defining which standards an engine must meet and when, we believe that
it is critical that a singular power value be determined objectively
according to a specific regulatory definition.
    For locomotives, the term ``rated power'' will continue to be used,
but would be explicitly defined to be the brakepower of the engine at
notch 8. We would continue to use the term ``rated power'' because this
definition is consistent with the commercial meaning of the term.
    We are also adding a clarification to the regulations for both
locomotives and marine engines to recognize that actual engine power
varies to some degree during production. Manufacturers would specify
maximum engine power (or rated power for locomotives) based on the
design specifications for the engine (or locomotive). Measured power
from actual production engines would be allowed to vary from that
specification to some degree based on normal production variability.
The expected production variability would be described by the
manufacturer in its application. If the engines that are actually
produced are different from those described in the application for
certification, the manufacturer would be required to amend its
application.
    Finally, we are requesting comment on whether we need to specify
more precisely how to determine alternator/generator efficiency for
locomotive testing. In locomotive testing, engine power is not
generally measured directly, but rather is calculated from the measured
electrical output of the onboard alternator/generator and the
alternator/generator's efficiency. Thus, it is important that the
efficiency be calculated in a consistent manner. Specifically, we are
requesting comment on whether to require that the efficiency be