UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
 WASHINGTON, D.C. 20460

 OFFICE OF
 ENFORCEMENT AND
 COMPLIANCE ASSURANCE

 September 4, 1997

 Addendum to Mobile Source Enforcement Memorandum 1A

SUBJECT: Tampering Enforcement Policy for Alternative Fuel
Aftermarket Conversions 

A. Purpose The purpose of this document is to clarify and
revise the U.S. Environmental Protection Agency's (EPA's)
"tampering" enforcement policy for motor vehicles and motor
vehicle engines originally designed to operate on gasoline or
diesel fuel and subsequently modified to operate exclusively or
in conjunction with compressed natural gas (CNG) or liquified
petroleum gas (LPG or propane), hereinafter referred to as
"alternative fuels". The provisions of this Addendum shall
apply to all persons subject to the tampering prohibition of
Section 203(a) of the Act. For the purpose of this policy
Addendum, the term "manufacturer" will apply to any person who
designs, produces, and/or assembles components for converting
vehicles or engines to operate on alternative fuels and is
responsible for complying with all applicable requirements of
this policy Addendum.

B. Background: EPA's policy is and has been that any
alteration from an original configuration of a vehicle or engine
as certified under Title II of the Act may constitute tampering
under Section 203(a)(3). Routine maintenance and repair of
vehicles and engines requires the use of replacement parts which
may be non-original or "aftermarket" parts or systems. EPA's
Office of Enforcement and General Counsel issued Mobile Source
Enforcement Memorandum 1A (Memo 1A) on June 25, 1974 to provide
guidance to covered parties regarding how the Agency intended to
enforce the "tampering" prohibition under Section 203(a)(3) of
the Clean Air Act (Act) with respect to maintenance and the use
of aftermarket parts. 

 Memo 1A provides, in part, that the use of an aftermarket
part, alteration or add-on part will not constitute tampering if
the dealer has a "reasonable basis" to believe that such acts
will not adversely affect emissions performance. It also
provides specific procedures or options by which the dealer would
have a "reasonable basis". One available procedure is emissions
testing performed in accordance with "40 CFR 85" (subsequently
revised and incorporated under 40 CFR Part 86) demonstrating
compliance with emission standards for the useful life of the
vehicle or engine. An alternate option is that "a Federal, state
or local environmental control agency represents that a
reasonable basis exists" based on testing done in accordance with
procedures specified by that agency. Many vehicles converted
from gasoline fueled to CNG or propane have relied on the second
option utilizing procedures established by California or Colorado
for demonstrating emissions compliance. 

 EPA has recently become aware of federal emission test data
generated under a program conducted by the National Renewable
Energy Laboratory (NREL) which indicate that a significant number
of these vehicles modified to run on alternative fuels may be
exceeding one or more applicable federal emission standards. 
The installers involved in the NREL program had attempted to
comply with Memo 1A by using conversion systems certified by the
state of California under the "California Exhaust Emission
Standards and Test Procedures for Systems Designed to Convert
Motor Vehicles Certified for 1993 and Earlier Model Years to Use
Liquefied Petroleum Gas or Natural Gas Fuels" (pre-1994
California Procedures). EPA has subsequently reviewed emission
test data from other sources which generally substantiate the
NREL results. 

 In response to concerns raised by these data, the Agency
conducted a public stakeholders meeting on February 21, 1997,
with representatives of the affected industries, regulatory
agencies and interested fleet operators. The purpose of the
meeting was to discuss these data and the causes of the emission
failures as well as to explore all available options to identify
and remedy the problems. Many reasons were provided for the
emission problems, including inadequate initial testing,
insufficient durability evaluations, overly broad vehicle
application based on limited testing, inadequate systems/parts
specifications, improper installation and fuel variability. The
concerns of the affected industries and fleets subject to several
alternative fuel statutory mandates were also discussed. 
 
 The most significant conclusion reached at that meeting, and
from extensive data review and discussions subsequent to that
meeting, was that the pre-1994 California and Colorado procedures
as currently structured do not provide an adequate demonstration
or assurance that a vehicle or engine modified to operate on an
alternative fuel using an aftermarket conversion system will
comply with the applicable emission standards for its useful
life. As a result of the above and in light of the number of
vehicles and engines that may be converted to alternative fuels
in the near future, EPA believes it is appropriate to issue this
Addendum to Memo 1A (this Addendum) to provide additional
guidance to the regulated community, including manufacturers and
installers of alternative fuel conversion systems.

C. Revised Policy: Effective immediately, EPA will no longer
accept a representation based on the pre-1994 California
Procedures for alternative fuel conversion systems or on the test
procedures under Colorado Regulation No. 14 in effect prior to
the date of this Addendum as a "reasonable basis" under paragraph
3(c) of Memo 1A. Consequently, any future installation of an
alternative fuel conversion system, or the modification of any
motor vehicle or motor vehicle engine in compliance with Title II
of the Clean Air Act to operate exclusively or in part with an
alternative fuel, or the causing thereof, may constitute
tampering under Section 203(a) of the Act, where the installer or
manufacturer has relied exclusively on a representation by
Colorado or California, as described above, that a reasonable
basis exists in accordance with paragraph 3(c) of Memo 1A. 
Effective immediately, the "reasonable basis" under paragraph 3
of Memo 1A that EPA agrees may be relied on by any person,
including a manufacturer, installer or operator, when converting,
or causing the conversion of, a motor vehicle or motor vehicle
engine to operate on an alternative fuel is limited to one of the
three options listed below. 

 1. A Federal Certificate under 40 CFR Part 86
demonstrating compliance with the applicable standards or under
40 CFR Part 88 demonstrating compliance with Clean Fuel Fleet
standards for each engine family to be converted in accordance
with 40 CFR Part 85, Subpart F; or
 
 2. A Retrofit System Certification under the "California
Certification and Installation Procedures For Alternative Fuel
Retrofit Systems for Motor Vehicles Certified for 1994 and
Subsequent Model Years" for a conversion system installed and
tested under the above procedures on a vehicle or engine from a
"50-state engine family" for use nationwide, or for a conversion
system installed and tested under the above procedures on a
vehicle or engine from a "California engine family" for use in
California only; or

 3. Until December 31, 1998, the use of an alternative fuel
conversion system designed, tested and installed on a single
engine family, or multiple engine families as provided under
paragraph b.(4) below, if testing is completed by March 31, 1998,
as follows:

 a. With the alternative fuel conversion system
installed on the certified engine family, the manufacturer shall
perform, or cause the performance of, one federal emission test
while operating with the alternative fuel and one test with the
original certification fuel, if dual fuel operation is retained,
in accordance with the applicable test procedures under 40 CFR
Part 86 or Part 88 for that class and model year vehicle or
engine. Prior to testing, the vehicle or engine shall be
operated with the conversion system installed for at least the
number of miles or hours equal to the service accumulation period
needed to stabilize the emission control system specified by the
original manufacturer in its certificate application submitted to
EPA. EPA encourages manufacturers to conduct at least one
baseline emission test with the certification fuel prior to
conversion to ascertain that the vehicle or engine meets the
applicable standards. 
 
 b. (1) With the application of an appropriate
deterioration factor (DF) to the above test results, the vehicle
or engine shall meet the applicable federal exhaust emission
standards to which the vehicle or engine was originally
certified. The DF shall be determined either based on full
useful life durability testing, predictions based on engineering
judgement for a similar light duty vehicle or heavy-duty engine
with a similar emission control system using the same alternative
fuel conversion system, or determined in accordance with the
appropriate protocol contained in the "Dear Manufacturer" letter
of September 27, 1995 - Assigned Deterioration Factors for
Gaseous-Fueled Vehicles and Engines, identified as CD-95-14. For
heavy-duty engines with aftertreatment (such as a catalyst), the
deteriorated emissions are calculated by multiplying the DF with
the exhaust emission results. For heavy-duty engines without
aftertreatment, the deteriorated emissions are calculated by
adding the DF with the exhaust emission results. For a vehicle
or engine converted and tested prior to accumulating 50% of its
useful life, the manufacturer shall apply the full DF. For a
vehicle or engine converted and tested subsequent to accumulating
50% of its full useful life, apply a DF that is the midway point
between no DF and the full DF. For example, an additive DF of
1.0 may become 0.5 and a multiplicative DF of 2.0 may become 1.5. 
For a vehicle or engine converted and tested subsequent to
accumulating its full useful life, apply no DF.

 (2) For heavy-duty engines used in vehicles with
a gross vehicle weight rating (GVWR) less than or equal to 10,000
lbs, the manufacturer may demonstrate compliance with the
applicable light-duty truck standards in accordance with the
preceding paragraph.
 
 (3) In lieu of engine dynamometer testing for on-
highway heavy duty vehicles with a GVWR less than or equal to
14,000 lbs, the manufacturer may conduct two or three emission
tests as described below in accordance with the most current
amendments to "California Exhaust Emissions Standards and Test
Procedures for 1988 and Subsequent Model Passenger Cars, Light-
Duty Trucks and Medium-Duty Vehicles". These shall consist of
one baseline test using the certification fuel prior to
conversion, one test after conversion with the alternative fuel
and one test after conversion with the certification fuel if the
vehicle is intended to be dual fuel. The two tests after
conversion shall not result in any exhaust emissions that exceed
1.10 times any of the baseline emission levels. In the case of
pure CNG operation, the after conversion NMHC emissions shall not
exceed 0.9 times the THC emissions before conversion. For heavy-
duty vehicles operating on a mixture of CNG and either diesel
fuel or gasoline, the conversion system manufacturer should
contact EPA's Mobile Source Enforcement Branch to determine the
appropriate ratio of NMHC emissions after conversion to THC
emissions before conversion.

 (4) With respect to light duty vehicles, light
duty trucks, or heavy-duty engines meeting the requirements of
paragraph (2) above, the above demonstration may be applied as a
reasonable basis for up to a maximum of three additional light
duty engine families to that tested, provided:

 A. The results from testing done in accordance with
the above procedures demonstrate compliance with low emission
vehicle (LEV) or more stringent emission standards under 40 CFR 
88.104,

 B. The additional engine families have engine
displacements equal to, or within 0.8 liters (50 CID) less than,
the engine tested, 

 C. The additional engine families comprise vehicles
equal to or less than the gross vehicle weight of the vehicles
covered by the engine family tested, and

 D. The additional engine families are equipped with
the same catalytic converter type (i.e. beaded vs monolith, OC vs
OC/RC) and the same primary emission control technology (eg. EGR,
Air Injection, EFI vs carburetor, closed loop vs open loop) as
the engine family tested.
 
 (5) Option 3 of this policy is not available for
conversion of California only engine families.

 (6) An alternative fuel conversion system that
degrades a closed loop feedback system to a continuous non-
feedback open loop system is not allowed under this option.
 
 (7) Compliance with this policy may be
demonstrated based on existing data provided such data are the
result of testing in accordance with the procedures and protocols
specified herein.
 
 (8) Demonstration with the Cold CO requirements
under 40 CFR Part 86 Subpart C is not required under Option 3 of
this policy.


 (9) The Certification Short Test requirements
under 40 CFR Part 86, Subpart O is not required under Option 3 of
this policy.

 (10) The evaporative emissions requirements under
40 CFR 86.094-8(b) and 86.094-9(b) are not required under Option
3 of this policy. 

 c. The manufacturer of the conversion system shall
specify all part numbers/calibrations associated with that
conversion system and provide all such information,
specifications and installation requirements, including a
permanent conversion system label which appropriately identifies
the conversion system with reasonable specificity, with each
system that is sold or provided for installation.

 d. In order to demonstrate that it has a reasonable
basis to believe that its conversion system will not adversely
affect emissions over the useful life of the vehicle or engine,
the conversion system manufacturer should retain records
including but not limited to all emission test data, including
test results, description of vehicles and/or engines modified,
all maintenance and modifications performed, laboratory data
sheets, identification of test laboratory, test dates, test
personnel and test procedures followed, engine families tested,
data to support additional engine family coverage, if applicable,
VIN's, vehicle and engine mileage and/or age as applicable, fuel
specifications, conversion system part numbers and calibrations,
durability procedures followed including all durability data and
all calculations and engineering analyses performed to determine
compliance with the above requirements.
 
 e. In order to meet the requirements of this policy,
any installation of a conversion system designed and tested in
accordance with the above shall be done in accordance with the
applicable part numbers/calibrations installed on the vehicle or
engine that was tested, completed in accordance with
manufacturer's specifications and/or instructions and the
conversion system label affixed to the vehicle or engine. The
system shall only be installed on a vehicle or engine of the same
engine family as that tested or as permitted under paragraph
3.b.(3) above.
 
 f. In support of an appropriate installation, the
installer should retain records of each vehicle or engine
converted in accordance with the above, including the VIN, make
and year of each vehicle or engine so modified, the name of the
installer, the date of installation and a copy of the
manufacturer's or marketer's/distributor's representation that
the conversion system has been demonstrated on that engine family
to meet the requirements of this policy

 g. In support of any marketer's or distributor's
compliance with the requirements of this policy, such parties
should retain records of each conversion system sold or
distributed, copies of the representation from the manufacturer
that the system meets this policy and records of sales to others
including the name of the purchasers, part numbers, dates of
sales and the numbers of systems sold.

 h. Colorado has indicated that it will revise its
administrative procedures under Colorado Regulation No. 14 to
require that conversion system manufacturers conduct testing in
accordance with option 3 of this Addendum in order to receive a
Colorado Letter of Certification. Consequently, until December
31, 1998, EPA will not consider as tampering the sale and
installation of a conversion system in Colorado pursuant to a
Colorado Letter of Certification issued after the above-
referenced administrative procedure revisions have been made by
Colorado, provided testing in support of the Letter of
Certification is done in accordance with option 3 of this
Addendum and is completed by March 31, 1998.

 
D. Conclusion: EPA believes that the maximum degree of
assurance that vehicles or engines modified to operate on
alternative fuels will meet emissions standards throughout their
useful life can only be achieved through full certification
demonstration in accordance with 40 CFR Parts 86 or 88. However,
the cost and time associated with such a demonstration may be
prohibitive for some conversion system manufacturers in the short
term and may not provide sufficient equipment for fleets
currently subject to various alternative fuel mandates to comply
with those mandates. In addition, EPA will be attempting to
implement various procedures to streamline federal certification
for alternative fuel vehicles and on-highway engines, but it is
likely that implementation of those procedures will take some
time. In the interim, the procedures and requirements outlined
in option 3 above should allow alternative fuel conversion
systems to be developed and evaluated more quickly and at less
cost, while providing a reasonable assurance that emissions will
not be deteriorated. After December 31, 1998, manufacturers,
marketers and installers must utilize equipment which meets the
requirements of option 1 or option 2 above to be covered by the
non-tampering policy of Memo 1A. 

 EPA will be reviewing Memo 1A more thoroughly in the near
future to determine if additional changes are required for other
vehicle or engine modifications, parts or systems. Any
questions regarding this interim policy should be directed to the
Mobile Source Enforcement Branch at (202) 564-2255.


 /s/

 Bruce C. Buckheit, Director
 Air Enforcement Division
 Office of Enforcement and Compliance Assurance