Retrofit/Rebuild Requirements for 1993 and Earlier Model Year Urban Buses; Approval of a Notification of Intent to Certify Equipment

ENVIRONMENTAL PROTECTION AGENCY

[FRL-5672-8]

Retrofit/Rebuild Requirements for 1993 and Earlier Model Year

Urban Buses; Approval of a Notification of Intent to Certify Equipment

AGENCY: Environmental Protection Agency.

ACTION: Notice of Agency Certification of Equipment for the Urban Bus

Retrofit/Rebuild Program.

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SUMMARY: The Agency received a notification of intent to certify

equipment signed December 13, 1995, from Engine Control Systems Ltd.

(ECS) with principal place of business at 165 Pony Dr., Newmarket,

Ontario, Canada L3Y7V1 for certification of urban bus retrofit/rebuild

equipment pursuant to 40 CFR 85.1401-85.1415. The equipment is

applicable to petroleum-fueled Detroit Diesel Corporation (DDC) two-

cycle engines originally installed in an urban bus from model year 1979

to model year 1993, exclusive of the DDC 6L71TA 1990 model year

engines, all alcohol fueled engines, and models which were manufactured

with particulate trap devices (see Table A). On August 8, 1996 EPA

published a notice in the Federal Register that the notification had

been received and made the notification available for public review and

comment for a period of 45 days (60 F1 41408). EPA has completed its

review of this notification, and the comments received, and the

Director of the Engine Programs and Compliance Division has determined

that it meets all the requirements for certification. Accordingly, EPA

approves the certification of this equipment.

The certified equipment provides 25 percent or greater reduction in

exhaust emissions of particulate matter (PM) for the engines for which

it is certified.

The ECS notification, as well as other materials specifically

relevant to it, are contained in Public Docket A-93-42, category XIV-A,

entitled ``Certification of Urban Bus Retrofit/Rebuild Equipment''.

This docket is located in room M-1500, Waterside Mall (Ground Floor),

U.S. Environmental Protection Agency, 401 M Street SW, Washington, DC

20460.

Docket items may be inspected from 8:00 a.m. until 5:30 p.m.,

Monday through Friday. As provided in 40 CFR Part 2, a reasonable fee

may be charged by the Agency for copying docket materials.

DATES: The effective date of certification is established in a letter

to ECS dated December 9, 1996 for the equipment described in the ECS

notification. This certified equipment may be used immediately by urban

bus operators. Operators who have chosen to comply with program 1 or

program 2 can utilize this equipment or other equipment that is

certified for any engine that is listed in Table A that undergoes

rebuild.

FOR FURTHER INFORMATION CONTACT: Anthony Erb, Engine Compliance

Programs Group, Engine Program & Compliance Division (6403J), U.S.

Environmental Protection Agency, 401 M St. SW, Washington, D.C. 20460.

Telephone: (202) 233-9259.

SUPPLEMENTARY INFORMATION:

I. Background

By a notification of intent to certify signed December 13, 1995,

ECS applied for certification of equipment applicable to petroleum-

fueled Detroit Diesel Corporation (DDC) two-cycle engines originally

installed in an urban bus from model year 1979 to model year 1993,

exclusive of the DDC 6L71TA 1990 model year engines and models which

were manufactured with particulate trap devices or alcohol fueled (see

Table A). The notification of intent to certify states that the

equipment being certified is an oxidation converter muffler (OCM). The

OCM contains an oxidation catalyst developed specifically for diesel

applications, packaged as a direct replacement for the muffler. The

application demonstrates that the candidate equipment provides a 25

percent or greater reduction in emissions of particulate matter (PM)

for petroleum fueled diesel engines relative to an original engine

configuration with no after treatment installed. Certification is

applicable to engines that are rebuilt to original specifications, or

in-use engines that are not rebuilt at the time the OCM is installed

provided the engine meets engine oil consumption limits specified by

ECS. ECS is also certifying a 25 percent reduction in PM for engines

that are retrofit/rebuilt with certified rebuild kits that do not

include after treatment devices if the OCM is installed at the same

time the retrofit/rebuild occurs. Currently, this applies to the DDC

retrofit/rebuild kit which was certified on October 2, 1995 (60 FR

51472) for the 6V92TA MUI model and to the kit certified on July 19,

1996 (61 FR 37738) for the 6V92TA DDEC II model.

Certification of the OCM does not trigger any new program

requirements for applicable engines, because the requirement to use

equipment certified to achieve at least a 25% reduction has already

been triggered for these engines.

Using engine dynamometer testing in accordance with the Federal

Test Procedure for heavy-duty diesel engines on a 1991 DDC 6V92TA DDEC

II engine, ECS documented a 26% reduction in PM emission after

retrofit. The test results for this engine with the certified retrofit

equipment installed meet applicable Federal emission standards for

hydrocarbon (HC), carbon monoxide (CO), oxides of nitrogen (NOx), and

smoke emissions. In chassis testing performed over the Central Business

District (CBD) sequence on a 1987 DDC 6V71N engine, ECS demonstrated a

42% PM emission reduction after retrofit. Using chassis testing

performed over the New York Composite (NYC) sequence on this same

engine, ECS demonstrated a 37% reduction in PM emission.

Table A provides the PM emission certification levels for the ECS

equipment for the specified models and model years.

Table A.--Certification Levels

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

PM Level

\2\with OCM

Engine models Model year PM Level and DDC Code/Family

\1\ with Certified

OCM Rebuild kit

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

6V92TA MUI............................ 1979-87............. 0.38 0.22 All.

1988-1989........... 0.23 0.17 All.

6V92TA DDEC I......................... 1986-87............. 0.23 N/A All.

6V92TA DDEC II........................ 1988-90............. 0.23 0.17 All.

1991................ 0.23 N/A

1992-93............. 0.19 N/A All.

[[Page 747]]

6V71N................................. 1973-89............. 0.38 N/A All.

6V71T................................. 1985-86............. 0.38 N/A All.

6L71TA................................ 1988-89............. 0.23 N/A All.

6L71TA DDEC........................... 1990-91............. 0.23 N/A All.

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\1\ The original PM certification levels for the 1991 6V92TA DDEC II, and 6L71TA DDEC engine models are based on

Family Emission Limits (FELs)under EPA's averaging, banking and trading program (AB&T). These limits are

higher than the 1991 PM standard of 0.25 g/bhp-hr. The PM level listed in this table for the engines that are

equipped with the OCM provide at least a 25% reduction from the FEL. The 1992 to 1993 6V92TA DDEC II engine

models were also certified using FELs under the AB&T program and likewise the PM levels for the engines

equipped with the OCM represent at least a 25% reduction from the FEL.

\2\ For 6V92TA MUI and 6V92TA DDEC II models that are rebuilt using a certified DDC emissions retrofit kit, ECS

is certifying the PM engine emissions to reduced levels as provided in Table A. provided the OCM is installed

at the same time the rebuild with the certified DDC upgrade kit takes place. The DDC upgrade kit certification

notifications were published in the Federal Register on October 2, 1995 (60 FR51472) and July 19,1996 (61

FR37738) respectively.

Under Program 1, all rebuilds or replacements of applicable engines

must use equipment certified to reduce PM levels by at least 25

percent. This requirement will continue for the applicable engines

until such time as it is superseded by equipment that is certified to

trigger the 0.10 g/bhp-hr emission standard for less than a life cycle

cost of $7,940 (in 1992 dollars).

ECS has established PM certification levels as specified in Table A

for this equipment. Operators who choose to comply with Program 2 and

install this equipment, will use the specified PM emission levels in

their calculation of fleet level attained.

II. Summary and Analysis of Comments

EPA received comments from two parties on this notification. The

Detroit Diesel Corporation (DDC) had a number of comments in the

following areas: test engine selection, extrapolation of test results,

reductions in non-volatile particulate matter, certification of

equipment for use on different stages of engine rebuild, certified

emission levels, incomplete parts listing and representivity of test

data. The Engelhard Corporation commented on the following areas: worst

case demonstration, incomplete parts listing, representivity of test

data to cover all engines and types, and the ability of the OCM to

reduce PM emissions.

DDC stated that the test configuration of the 1991 DDC 6V92TA DDEC

II engine was not clearly documented and that the original

configuration of the test engine was a 1992 code 4T engine intended for

use with a particulate trap. DDC questioned the relevance of testing

performed on an engine with a unique calibration originally intended

for use on trap equipped engines. DDC noted that test data it developed

during new engine certification testing for the 1991 4C rating (a non-

trap configuration) had a total PM level of 0.218 g/bhp-hr with a

soluble fraction (SOF) of 21.5%. DDC questioned how this engine could

be considered ``worst case''. Given that oxidation catalysts primarily

reduce the SOF portion of PM, DDC questioned whether the OCM could

reduce PM emissions on the 1991 code 4C rating by 25% when the entire

SOF fraction is only 21.5%.

Based on the information presented by ECS, it is unclear whether

the engine rating at the time of testing was in the 4T or the 4C

configuration. It was not clear from ECS that the engine had been

converted from it's original 4T rating. Also, background historical

information for this engine could not be provided. Since there is

nothing in the record which indicates that the engine was converted to

the 4C configuration, the Agency assumes that it was tested in the

original 4T configuration. Therefore, it is apparent that DDC's

comments relative to SOF content of the 4C configuration relative to

the test performed on the 4T configuration would not be relevant in the

certification being discussed. However, it is noted that because an

oxidation catalyst mainly reduces only the SOF portion of PM, it would

not be possible to obtain a 25% reduction in PM for any engine for

which the SOF portion of PM is less than 25%. EPA requests information

from industry and the general public with regard to the percentage of

SOF that particular in-use engines produce. This information would be

considered for the certification being discussed in this notice and in

regard to the previous certifications of oxidation catalysts under the

urban bus retrofit/rebuild program.

In regard to DDC's and Engelhard's contention that the 1991 6V92TA

DDEC II engine would not represent the worst case according to the

regulations, EPA agrees. However, the 1987 6V71N does qualify as a

``worst case'' engine for testing purposes under the urban bus retrofit

regulations, and test results from this engine provide the basis for

the certification discussed herein.

DDC questioned the relevancy of the chassis dynamometer test

results obtained on the 6V71N engine using the Central Business

District (CBD) and New York Composite (NYC) cycles and noted that EPA

should not rely on the chassis test results in assessing whether the

OCM technology meets requirements to reduce PM emission by 25%. In

response, the regulations allow a certifier to use chassis based test

procedures representative of typical urban bus operation to show

compliance with the 25% or greater PM reduction requirement. The CBD

simulates stop and go performance of urban buses in the city and the

NYC was incorporated to represent some higher average speeds not seen

in the CBD which an urban bus may on occasion encounter. After review,

EPA found the proposed chassis testing plan to be acceptable and

approved the use of chassis testing to demonstrate the 25% reduction in

PM.

EPA agrees with the comment from Engelhard and DDC that it is

tenuous to base certification of OCMs, intended for engines using non-

particulate trap ratings, on testing where the 4T-trap based rating was

utilized. However, ECS provided acceptable chassis test results

performed on a non-trap engine that demonstrate reduction of PM by at

least 25%.

Engelhard also stated that the reduction of 26% demonstrated on the

[[Page 748]]

6V92TA DDEC II engine does not demonstrate a sufficient margin beyond

the 25% level to account for in-use deterioration of the catalyst over

the 150,000 mile performance warranty period. EPA finds that the

results of this test are not conclusive because the engine

configuration tested apparently does not represent an urban bus engine

that could be used to demonstrate PM reduction under the retrofit/

rebuild program since it was apparently in a calibration for a

particulate trap equipped engine. However, chassis testing data

presented by ECS shows a decrease in PM of at least 37% providing ample

margin beyond the required 25% reduction.

In the notification, ECS sought to use the OCM kit on engines which

were not in need of rebuild at the time of OCM installation based on a

review of specified engine conditions. DDC commented that certification

should be approved only with respect to engines that have been rebuilt

to original specifications as the retrofit/rebuild requirements do not

apply until the operator rebuilds an engine. DDC agreed that under

Program 2 operators could conceivably install certified add-on

equipment without rebuilding the base engine and use the certified

emission level in their fleet averaging, but expressed concerns that

the engine may have worn cylinders or fuel injection components in need

of rebuild and, as a result, the engine out PM emissions may be high.

DDC stated that engine wear conditions would create difficulty in

achieving the certification level when applying the OCM to an engine

which has not been rebuilt.

DDC's claim that program requirements do not apply until an

operator rebuilds an engine concerns compliance programs. Operators

choosing to comply with Program 1 are not required to take any action

until an affected engine is rebuilt or replaced. However, operators

choosing to comply with Program 2 must ensure their fleet is equal to

or less than their target fleet level at all times. Thus, program

requirements apply continuously to Program 2 operators. In addition, if

an operator desires to be able to change between programs, the

regulations require that both programs be complied with prior to the

switch.

While it is true that Program 1 requirements become effective when

the engine is rebuilt, EPA encourages the installation of certified

equipment prior to the time it is required under the regulations in

accordance with the manufacturer's instructions.

In regard to DDCs' concern that engine wear needs to be evaluated

prior to installing this equipment, ECS has modified its application to

remove the language referring to ``specified engine calibrations''

which DDC stated was vague and unenforceable and will instead require

that operators determine the oil consumption rate for an engine to

determine engine wear and condition prior to installing the OCM. If the

rate of oil consumption exceeds 1.5 quarts of consumption per 10 hours

of operation, ECS will require that the engine be rebuilt prior to OCM

installation. Furthermore, ECS is responsible for meeting the

performance warranty for a period of 150,000 miles for each engine

under this certification. EPA believes that operators will rebuild

engines when necessary in order to keep their fleet in reasonable

operating condition. The decision to rebuild will not be affected by

the option to install a catalyst. Rather, operators will only choose to

install the catalyst in order to reduce emissions, and not in place of

a needed rebuild. It is noted that the chassis testing data presented

demonstrates a 37% to 42% reduction in the case where the engine was

rebuilt. Based on these levels of reduction, it is apparent there

should be ample margin between the in-use emissions of an engine that

the operator finds is not in need of a rebuild to reasonably project

that the levels stated in Table A can be met.

DDC questioned reported reductions in the non-volatile PM fraction

with the OCM, noting that it is commonly accepted that oxidation

catalysts are effective in oxidizing volatile particulate, but have

little effect on the non-volatile component. In response, ECS explains

that effective diesel oxidation catalysts will have some activity

towards reduction of the non-volatile or insoluble portion of diesel

particulate. This activity allows the catalyst to clean itself from

carbon build-up and prevents catalyst fouling, particulate build-up and

eventual plugging of the substrate. ECS also stated that it is

important to recognize that, in the measurements taken, the volatile

organic fraction and non-volatile organic fractions were made using the

direct filter injection gas chromatography analysis DFI/GC technique

developed by Southwest Research Institute. Using this procedure some

small amount of high molecular weight solubles that did not volatize

may exist in the unvolatized particulate sample which would account for

the reduction seen. ECS stated that since diesel engine oxidation

catalysts all operate on the same basic principle, the points being

made relative to volatile vs. non-volatile components of urban bus PM

emissions apply to the industry as a whole and should not be confined

to the ECS certification review process. EPA concurs that this issue

should be addressed on an industry-wide basis. Further, EPA does not

have sufficient information to resolve this issue based on the comments

submitted. Therefore, EPA requests that industry and the public provide

any additional information on this matter so that resolution may be

reached in the future.

DDC and Engelhard commented that the rebuild on the 6V71N engine

appeared to be incomplete. DDC noted that the rebuild performed did not

include fuel injectors, piston rings, or cylinder liners all of which

would be replaced during a normal rebuild and which, if not replaced,

would cause inflated PM levels. DDC stated that if the Agency is to

rely on the chassis test data for certification of the OCM, it should

first make certain that it was properly rebuilt to the original engine

configuration prior to the testing. In response, ECS has provided

additional documentation that the piston rings, cylinder liners and

injectors were replaced at the time of rebuild and that the engine was

rebuilt to standard specifications. The failure to include this in the

original notification materials was an oversight.

With regard to certified emission levels, DDC commented that the

proposed certification levels do not represent a full 25% reduction.

For example, for the 1991 6V92TA DDEC engine codes 3C and 4C, the

original certification testing yielded PM emission levels of 0.25 and

0.22 g/bhp-hr, respectively, and the proposed certification level of

0.23 g/bhp-hr given in Table A represents only a 8% reduction on

average from the original certification test levels.

In response, the pre-rebuild levels listed in section 85.1403

(c)(1)(iii)(A) were determined by EPA based on certification results or

engineering data and judgement. In Table A, of today's notice, ECS has

listed the PM levels to which it is certifying for listed models and

years. In a number of instances the certification levels shown

represent a 25% reduction from the pre-rebuild levels that were listed

in section 85.1403(c)(1)(iii)(A) or the regulations. In other

instances, the number reflects a 25% reduction from the level that was

certified by DDC during new engine certification.

In the case of the 1991 6V92TA DDEC II 4C engine configuration, the

new engine certification testing by DDC yielded a PM emission level of

0.22 g/bhp-hr. However, DDC certified the engine to a family emission

level (FEL)

[[Page 749]]

of 0.30 g/bhp-hr. The certification level of 0.23 g/bhp-hr PM provides

for more than a 25% reduction from the original DDC certification level

or FEL for this engine and from the pre-rebuild level of section

85.1403(c). In previous urban bus retrofit/rebuild certifications, EPA

has based certification on the FEL which the original manufacturer

certified to meet in-use. In fact, the ECS certification levels for the

models listed are identical to those for which oxidation catalyst kits

have been certified to date. In declaring a FEL, the engine

manufacturer states the emission level it will achieve in-use. That is

to say, even though the certification test level is determined, the

engine manufacturer declares a different emission level that it can

meet in-use. Because the urban bus retrofit/rebuild program applies to

in-use buses, and since the rebuild certifier is certifying that a

rebuilt engine with the retrofit equipment will meet the rebuild

certification level during the warranty period, it makes sense to apply

the in-use certification level or FEL as a basis for the reduction. To

require certifiers of urban bus retrofit/rebuild equipment to reduce

emissions from an initial level that the original manufacturer did not

use during the original certification would not be reasonable. As

stated, EPA used the FEL as a basis for the 25% reduction in previous

decisions. EPA does not believe it would be reasonable to change the

basis for the 25% reduction as DDC has requested.

DDC noted that in order to ensure optimum engine performance,

emissions durability and fuel economy, DDC specifies maximum exhaust

back pressure limits for all DDC engines. DDC noted that there was a

small backpressure increase during testing and questioned whether the

catalyst used in testing had been aged prior to the test. DDC also

noted that the instructions to be given to operators did not include

backpressure specifications or procedures for checking backpressure

after the catalyst is installed. ECS has stated that careful attention

will be paid to optimizing the exhaust backpressure to a level

comparable to the original muffler. The catalyst used during testing

was aged or degreened to provide representative in-use performance. ECS

stated that it does not anticipate that checking the backpressure

should be required under normal circumstances. However, the converter

mufflers certified in this notice and produced by ECS include a port to

allow in-use backpressure checks and ECS has developed a procedure for

checking and cleaning the converter muffler that will be distributed to

operators who purchase the kit.

DDC commented that EPA should seek assurances that the certified

hardware will be available for all engine bus combinations. ECS has

indicated it has completed design work on the majority of converter

mufflers required for this market. If any specific design should be

encountered for which a converter muffler cannot be provided which will

meet the performance criterion, it will be reported to EPA. This

coupled with the fact that other companies have already certified

equipment for the engines covered under this application should provide

adequate coverage of the marketplace.

Engelhard commented that because thermal insulation was required on

the pre-catalyst exhaust on testing performed on the 6V92TA DDEC II

engine, insulation should be required on all pre-catalyst components

for ECS converter mufflers to be covered by certification. In response,

ECS explained that no insulation was used during the chassis tests

performed on the 6V71 engine for which PM reductions were demonstrated.

Insulation of the exhaust system is not necessary for OCM installation

on 6V71, 6V92 and 6L71 mechanical engine families as the exhaust

temperatures are sufficient for proper unit function. For the engine

dynamometer testing performed on the 6V92TA DDEC II engine, the entire

exhaust system was insulated. ECS subsequently performed additional

testing which indicates that the temperature loss between the

turbocharger and converter muffler is insignificant and that insulation

on the piping between the turbocharger outlet and the converter muffler

is not needed. However, ECS has determined that the actual converter

muffler must be insulated in order to maintain minimum catalyst

temperature for the DDEC II engine. Accordingly, ECS has designed all

converter mufflers for use on these engines to include either

insulation located within the muffler shell or via an external wrap/

blanket over the muffler casing.

Engelhard raised a concern based on the different exhaust

temperature profiles and engine out emissions that exist relative to

engines that are naturally aspirated, turbo charged or turbo-charged

after-cooled engines. Engelhard questioned whether an engine that

achieves a 25% reduction on a naturally aspirated engine could achieve

the same on a turbo-charged engine. Engelhard stated that without a

demonstration that 25% reduction in total PM could be obtained on all

versions of the 6V71, engine certification should not be granted for

all engines. Unfortunately, while Engelhard raised some interesting

questions in this area, it did not provide any data or information on

catalyst efficiency as it relates to different temperatures that could

be used to substantiate its claim. At this point, EPA does not have

information which would lead it to conclude that the ECS catalyst would

not be able to provide the 25% reduction on the models it has

identified. However, it is noted that in testing the 1991 6V92TA DDEC

II engine, ECS provides information that the OCM reduces emissions by

26% on an engine where the temperature reached a maximum of 320 degrees

Centigrade. These results address the concern relative to the ability

of the OCM to reduce PM emissions on engines that operate at the lower

end of the temperature spectrum. In regard to the issue of differing

emission rates, EPA needs information to conclusively deal with this on

an industry-wide basis and EPA welcomes such information from the

public and industry.

DDC commented that certification of the ECS equipment should not

cause DDC to have additional liability. DDC cited language in the

preamble to the final rule published in the Federal Register on April

21, 1993, page 21381. DDC's concern was centered around the following

statement, ``* * * However, if an engine manufacturer supplies

retrofit/rebuild equipment, it is responsible for the emissions

performance of the equipment.'' DDC suggested that it was EPA's intent

to make engine manufacturers accept additional liability for rebuild

hardware which they sell and which is subsequently used in a rebuild

which has been approved under the program. The statement simply means

that if the engine manufacturer supplies retrofit equipment as part of

a certified rebuild kit (such as the DDC certified upgrade kit) then

the manufacturer is responsible for the warranties associated with the

retrofit/rebuild regulations. If, on the other hand, the manufacturer

sells equipment for rebuild through its normal sales process, and such

sale is not part of a certified kit with which the manufacturer is

affiliated, the manufacturer is not liable for equipment performance

beyond its normal liability. That is to say, for equipment not sold by

the manufacturer to be included in a certified kit under the retrofit/

rebuild program, the manufacturer is not responsible for the defect

warranty or the performance warranty that is associated with the

retrofit/rebuild program. The retrofit/rebuild equipment

[[Page 750]]

certifier, however, is responsible for these warranties.

III. Certification Approval

The Agency has reviewed this notification, along with comments

received from interested parties, and finds that the equipment

described in this notification of intent to certify:

(1) Reduces particulate matter exhaust emissions by at least 25

percent, without causing the applicable engine families to exceed other

exhaust emissions standards;

(2) Will not cause an unreasonable risk to the public health,

welfare, or safety;

(3) Will not result in any additional range of parameter

adjustability; and,

(4) Meets other requirements necessary for certification under the

Retrofit/Rebuild Requirements for 1993 and Earlier Model Year Urban

Buses (40 CFR Sections 85.1401 through 85.1415). The Agency hereby

certifies this equipment for use in the urban bus retrofit/rebuild

program as discussed below in section IV.

IV. Operator Requirements and Responsibilities

This equipment may be used immediately by urban bus operators who

have chosen to comply with either Program 1 or Program 2, but must be

properly applied. Currently, operators having certain engines who have

chosen to comply with Program 1 must use equipment certified to reduce

PM emissions by 25 percent or more when those engines are rebuilt or

replaced. Today's Federal Register notice certifies the above-described

ECS equipment as meeting that PM reduction requirement. Only equipment

that has been certified to reduce PM by 25% or more may be used by

operators with applicable engines who have chosen Program 1. Urban bus

operators who choose to comply with Program 1 may use the certified ECS

equipment (or other certified equipment) until such time as the 0.10 g/

bhp-hr standard is triggered for the applicable engines.

Operators who choose to comply with Program 2 and use the ECS

equipment will use the appropriate PM emission level from Table A when

calculating their fleet level attained (FLA).

As stated in the program regulations (40 CFR 85.1400 through

85.1415), operators are required to maintain records for each engine in

their fleet to demonstrate that they are in compliance with the program

requirements beginning January 1, 1995. These records include purchase

records, receipts, and part numbers for the parts and components used

in the rebuilding of urban bus engines.

Richard D. Wilson,

Acting Assistant Administrator for Air and Radiation.

[FR Doc. 97-41 Filed 1-3-97; 8:45 am]

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