EPA-420-S-91-100
                                                Docket Number: A-87-11
                                                Document Number: 76) 1V-A
               Summary  of  Changed Circumstances
Control of Air Pollution From New Motor Vehicles and New Motor
Vehicle Engines;  Refueling Emission Regulations for Gasoline-
 Fueled Light-Duty Vehicles and Trucks and Heavy-Duty Vehicles
                          August 1991
           Standards  Development and Support Branch
             Emission Control  Technology Division
                   Office  of Mobile Sources
                  Office of Air and Radiation
             U.S. Environmental  Protection Agency

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     On August  19,  1987  EPA published in the  Federal  Register a
Notice of Proposed  Rulemaking (NPRM)  for the  control  of vehicle
refueling emissions  (52  FR 31162).   This  document  provides  a
summary  of  relevant  changed  circumstances  since  the  NPRM  was
published.  Section  I details the changed  circumstances  and Section
II  provides  a  discussion   of   the   impact  of  these  changed
circumstances on the proposed action.

     The changed  circumstances discussed in this  document arise
from three  sources.   First,  the  1990  Clean Air  Act  Amendments
(CAAA)  include  changes to the provisions related  to onboard and
Stage II  controls.   Second, technology  developments and several
recent/pending regulatory actions have potential effects on EPA's
analyses related to onboard controls.   Third,  comments received
following issuance  of the  NPRM  indicate  that  changes may  be
appropriate  for several aspects of the proposal.


I. Changed Circumstances

     This  section  discusses  the  changed  circumstances  since
issuance of the NPRM.   The  first portion discusses proposed or
final  regulatory actions and  technology improvements.   These
include fuel volatility control requirements, the requirements for
improved  evaporative   emissions  control,   and   vapor  control
technology improvements.  The second portion  addresses  changes due
specifically  to enactment  of the 1990  CAAA,   including onboard
applicability,   the   level   of   the   emission   standard,   and
implementation  leadtime.    The  third  portion  discusses  test
procedure changes  which  may be  appropriate,  based  on comments
received  on the  NPRM and  the  proposed changes  in evaporative
emission test procedures.

A. Fuel Volatility Regulation

     The regulation  of gasoline fuel volatility was proposed at the
same time as the August  1987 onboard  proposal.  However, because
the  specific  requirements  for volatility control had  not  been
finalized at that time, EPA's onboard analysis assumed that onboard
designs would be based on a fuel  volatility of  11.5 psi Reid vapor
pressure (RVP).   EPA has since promulgated a final rule  requiring
that, beginning in 1992,  fuel volatility be limited to a maximum of
9.0 psi RVP  in the summer months, when control of ozone-producing
emissions (including  refueling vapors)  is  most critical  (55 FR
23658,  June 11, 1990).   Fuel volatility  of  7.8 psi RVP  is called
for  in  some  southern  nonattainment  areas.     The  volatility
specification for certification  test  fuel will remain at 9.0 psi
RVP, thus ensuring  that  in-use  fuel  volatility will  not exceed
design basis fuel volatility in the critical control months.

     These  controls affect  several areas of  the  analysis which
accompanied the  onboard control proposal.   The most significant

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effect  is  a  decrease  in  the  amount  of  refueling  emissions
generated.  Although there is  some variation among vehicles, there
will typically be a decrease of about 11 percent in the amount of
emissions to be controlled,  thus reducing the air quality benefit
of refueling controls somewhat.  However,  for onboard systems, this
also allows a reduction in canister size from that estimated in the
NPRM analysis.   Purge  requirements will also be  eased somewhat.
Because smaller canisters are less expensive and  easier to package,
it would be reasonable  to expect that overall costs would be lower.

B.   Improved Evaporative Emissions Control

     Section 202 (k)  of the  amended  Clean Air  Act  requires EPA to
promulgate  regulations  to  improve  the control  of  evaporative
emissions from gasoline-fueled motor vehicles.  These regulations
must ensure emissions control  during vehicle operation and over at
least 2 days of nonuse.  Even before the CAAA were finalized, EPA
had proposed changes to the evaporative test  procedure as part of
the original  proposal  to control  in-use fuel  volatility  (52 FR
31274, August 19,  1987).  This  was  supplemented by an additional
notice on  January  19,  1990  (55 FR  1914).  A  public  workshop was
held on  December  19, 1990  (55 FR 49914, December  3,  1990).   The
Agency plans to finalize the improved evaporative rulemaking this
year.

     Although improved evaporative system designs will ultimately
depend  on  the  test  procedure  requirements  and  the  control
strategies  elected  by the manufacturers,  it  is expected  that
canister sizes would need to be increased to handle increased vapor
loads, and that the purge  system would need to be  upgraded to
transport greater  amounts of  vapor  to the  engine.   Manufacturers
would also  need to ensure that  these greater  amounts of vapor do
not increase exhaust emissions above the standards.

C. Technology Improvements

     The technology analysis  provided in  the proposal projected
that most  onboard control  systems  would be  integrated  with the
evaporative emissions control  system, so that the implementation of
onboard controls was considered incremental to current evaporative
emissions control requirements.

     Onboard system concept  development and prototype testing since
the proposal  was  issued  have indicated  that  even further design
simplifications are possible.   Basic  components  of  a simplified
design are presented in an EPA memorandum,  dated December 22, 1988
(available  in  Public Docket No. A-89-18,  item  II-B-6),  and in a
number of other technical and briefing documents in Public Docket
No. A-87-11.   As  is discussed  in these technical  documents and
briefings, EPA has developed and tested a simplified onboard system
in a bench configuration  and has installed a version of this system
in a  late model passenger  car.   The  prototype system met EPA's

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proposed refueling emission standard and performed satisfactorily
in limited in-use testing.

D. Applicability of the Standard

1. Vehicle Classes Regulated

     The August, 1987  proposal  covers  gasoline-fueled light-duty
vehicles (LDVs), light-duty trucks  (LDTs), and heavy-duty vehicles
(HDVs).   The Clean  Air  Act,  Section 202(a)(6), as amended in 1990,
directs EPA to "promulgate standards under this section requiring
that new light-duty vehicles manufactured beginning in the fourth
model  year  after  the  model year  in  which the  standards  are
promulgated  and thereafter  shall  be   equipped  with  [onboard]
systems."   Light-duty  vehicles  are  explicitly included,  but no
specific language dealing with other vehicle classes is provided.
Section 223 of the amendments defines light-duty  vehicles as having
the Code of Federal Regulations definition in effect at the time of
enactment of the amendments  (see 40 CFR  86.082-2).

     The report of the joint House/Senate conference on the 1990
CAAA  contains no legislative history  specifically  dealing with
onboard  controls,  although  it  does  point  out   that  Title  II
provisions (which include the paragraph requiring onboard controls)
are generally based on  the House bill, H.R.  3030 (House Report No.
101-952, 101st  Congress,  2nd Session,  336).   The report  of the
House Committee on  Energy and Commerce  on H.R. 3030, dated May 17,
1990  (House Report  No.  101-490,  101st Congress,  2nd Session, 303),
contains wording similar to that of the  final 1990 CAAA on onboard
controls,  applying  the  requirement   to "new  light-duty  motor
vehicles".   The report  goes on to say that "the standards required
to be promulgated  under this paragraph  are to apply to  all new
passenger cars and all light-duty trucks," implying that the term
"light-duty motor vehicles" was  intended to  include LDVs and LDTs.

     The Chafee-Baucus  Statement of Senate Managers  is described by
its  authors  as "our best  effort to provide  the  agency  and the
courts with  the guidance  that  they will need  in the  course of
implementing and interpreting this complex act"  (136 Congressional
Record,  S16933, daily ed.,  October 27,  1990).  In it they describe
the Conference agreement to essentially  adopt the House provision
for  onboard  controls,  specifically  characterizing  the  House
provision as applying "to all new passenger vehicles and light-duty
trucks."

     The legislative  history discussed above suggests  that Congress
may have intended  that LDTs be  included within the  scope of the
onboard  requirements.    In addition,  Congress  did  not  preclude
imposition   of   onboard   controls   based  on  other   statutory
authorities.  Thus, onboard controls could be required for LDTs and
HDVs  based on the Clean  Air Act's general  authority  provision,
Section  202(a)(1),  which  states:    "The Administrator  shall by

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regulation prescribe (and from time to time revise)  in accordance
with the provisions of this  section,  standards  applicable to the
emission of  any  air pollution from  any  class or classes  of new
motor vehicles or new motor vehicle engines, which in his judgment
cause  or  contribute to,  air pollution  which may  reasonably  be
anticipated to endanger public health or welfare."

     It  is  estimated  that  LDTs  contribute  about  one-third  of
current total  refueling  emissions.   Exempting LDTs  from onboard
control  requirements  would  reduce  the  benefit  of the  program
correspondingly,  mitigated perhaps temporarily by the presence of
Stage  II  controls  in  some  non-attainment  areas.   Furthermore,
because many of these vehicles are very similar to LDVs in terms of
design, hardware, and usage, controls would be  similar.   This is
reflected in the  fact  that  these  vehicle  classes are  treated
together in  other provisions of  the 1990 CAAA.   The incremental
cost of onboard controls per light-duty truck is estimated in the
EPA memorandum on cost (referenced in Section I.C  of this document)
to be  slightly higher than  that  of a typical LDV.   This is more
than offset, however,  by fuel recovery credits.

     The refueling emissions contributed by HDVs are estimated to
be about 5 percent of the total.   Although much smaller than that
of LDVs and  LDTs,  this  is still a  significant  contribution when
viewed in the context of  the very  high  efficiency achievable by,
and  required  for,  onboard  controls.   In  addition,  many  of the
smaller  HDV  designs,  such  as class  lib  and  III  trucks,  are
essentially  extrapolations   of conventional   LDTs  and could use
similar control technology.  Furthermore, fuel system designs for
other  gasoline-fueled  HDVs  are   similar  to those  of  lighter
vehicles,  and so the approaches taken  to designing LDV and LDT
onboard systems could apply to these larger vehicles as well.

2. Fuel Type Considerations

     The  growing  interest  in  the  use  of  alternative  fuels
necessitates clarification of which vehicle fuel types are meant to
be subject to onboard refueling vapor  control requirements.  The
language in the 1990 CAAA is not  specific regarding fuel type and
so does not directly resolve this issue.

     Although the  1987  proposal  applied only to gasoline-fueled
vehicles,  it may  be  appropriate to broaden any onboard requirement
to other  fuel types.   This  would  be consistent  with  EPA's past
approach of establishing a level playing  field for all fuel types.
If such an approach were  taken, any  vehicles  which  use a fuel of
low enough volatility that they can  meet the  refueling emissions
performance  standard  without  onboard  control systems would,  of
course, not  be required to install such systems.   In some cases, it
may  be  feasible  to  waive  testing requirements  if  refueling
emissions are inherently low.  Vehicles designed to operate on more
than one  fuel type would need to  meet  the  refueling emissions

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standard under the  fuel  composition  conditions  with the greatest
refueling emissions.

E. Emission Standard

     The   statutory  changes  also   raise   the  issue   of  the
appropriateness  of  the  0.10 gram  per  gallon   (g/gal)  emission
standard originally proposed in  the 1987 NPRM.   The  1990 CAAA
require a minimum emission capture efficiency of  95 percent. As is
shown  below,   the  proposed  standard appears   to  satisfy  that
requirement.

     Using the refueling  emission rate equation developed by EPA
and the limiting values of the applicable parameters specified in
EPA's  refueling  test procedure,  the efficiency of  the proposed
standard is shown below:

     ER = 0.485 RVP + 0.884 TD - 0.0949 AT - 5.909
        = 0.485  (9.0) + 0.884 (81) - 0.0949 (+2) - 5.909
        =5.43 g/gal

     where:
           ER = the refueling emission rate in g/gal.
          RVP = Reid Vapor Pressure in psi.
           TD = Dispensed fuel Temperature in °F.
           AT =  (Tank Temperature - Dispensed fuel Temperature)
                    in °F.

     The efficiency is therefore calculated to be:
          1 -  (0.10 * 5.43) = 0.98 or 98%.

     In the August  1987 NPRM, certification useful  life, recall
testing, and  warranty periods were  proposed  to be  the same for
onboard refueling controls  as for other  elements  of the vehicle
emission  control system  (52 FR  31220,  August  19,  1987).   The
amendments to the Act require that,  with respect only to LDVs and
LDTs up to 3,750  Ibs.  loaded vehicle weight  and 6,000 Ibs. gross
vehicle weight rating, "in the case of any requirement of  [Section
202] which first becomes applicable after  enactment... the [useful
life]  period  shall  be  ten years   or   100,000 miles   (or  the
equivalent),  whichever first occurs,  with testing for purposes of
in-use compliance under  section  207  up to (but  not beyond)  seven
years or 75,000 miles  (or the equivalent),  whichever first occurs,"
unless otherwise  specified  (Section  202(d) (1) ) .   With respect to
all other vehicles and engines,  the periods are presumed to be the
same as above  unless  the Administrator  finds  that longer periods
are  appropriate.    Warranty periods  were  shortened by  the 1990
amendments to two years/24,000 miles  (or the equivalent) for most
emission control components including onboard  refueling systems
(Section  207(i)).   One  possible approach to  implementing these
provisions would be to make only the  changes to this rule required
to make it conform  to the CAAA.   Taking  this  approach would mean

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that, for heavier  LDTs  and HDVs, the  requirements  which existed
during the time of the NPRM would apply.

F.   Implementation Leadtime

     In its 1987 NPRM, EPA estimated, based on its past experience
with evaporative emission controls, that a minimum leadtime period
of two years would be required to design,  develop,  and adequately
test  onboard  refueling   systems.    EPA acknowledged  that  some
uncertainty existed in its estimate and discussed the possibility
of using a phase-in approach to reduce the certification burden and
provide  manufacturers  more  time to  address any  model-specific
safety concerns. Responding to EPA's proposal, most manufacturers
indicated that  a minimum  of  four years leadtime was necessary to
ensure safe implementation of onboard  controls.   Longer leadtime
was  also  recommended  by the  National Highway Traffic  Safety
Administration  (NHTSA),   which  stated  that  it  is   critical  for
manufacturers to receive  sufficient leadtime in order to minimize
safety risks.

     Congress addressed leadtime for light-duty vehicles, mandating
an  implementation  schedule  in  the  1990  CAAA.   The  Amendments
require  a  three year phase-in  (40,80,100 percent,  applicable to
each manufacturer's sales volume)  of  onboard  refueling controls on
new light-duty vehicles beginning in "the fourth model year after
the model year in which the standards are promulgated."  Because it
is probable that most vehicle models would  be in 1992 model year
production before the final rule  is promulgated,  an onboard phase-
in requirement  could not become effective before the  1996 model
year.

G. Refueling Test Procedure

     It is desirable  that  the onboard system test  procedure provide
an accurate assessment of the control of refueling emissions while
minimizing the testing burden on both industry and government.  The
ideas discussed below for  modifying the proposed test  procedure are
based on comments received on the NPRM and anticipated changes in
the evaporative test  procedure.  These alternative approaches, each
of which is discussed in  further detail below, are as follows: 1)
vehicles which have the onboard system  integrated with evaporative
control  systems would   use  all  or  part   of  the   Federal  Test
Procedure1 (FTP) as  the preconditioning cycle before a refueling
test; 2)  abbreviated preconditioning options would  be  added for
non-integrated  systems;  3)  an abbreviated procedure for testing
seals and connections would be added; 4) a four  gallon per minute
lower limit would be specified for the refueling dispensing rate.
     1 The  Federal Test  Procedure  (FTP)  refers  to  the testing
sequence that includes the exhaust and evaporative emission systems
test procedures.

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1.  Preconditioning  Fully-Integrated   and  Partially-Integrated
Systems

     The refueling test procedure proposed  in the August 1987 NPRM
for  fully-integrated   and  partially-integrated   systems   is  a
separate,   stand-alone  sequence   which   would   be   performed
independently from the FTP sequence.   It  consists of  a  vehicle
preconditioning sequence followed by the actual refueling emissions
measurement  test.    A   diagram  of  this  proposed   refueling  test
procedure is provided in Figure 1.

     A number of comments on the original onboard refueling control
proposal concerned the  complexity of  the test procedure.  Although
the  proposed procedure was   itself  the product   of  interaction
between EPA  and manufacturers,  it  still appeared  to  represent a
significant  increase  in impact  on  testing resources.    These
resource  impacts  were largely   associated with  the  vehicle
preconditioning sequence, which involved loading the vapor storage
canister to  at  least the breakthrough  point and  then simulating
three days of normal vehicle  driving.   Commenters suggested that
EPA should develop a simplified approach to refueling testing in
order to reduce the test's resource  impacts.  In  response to the
comments, the Agency undertook further study aimed at identifying
alternative methods for vehicle preconditioning which would be less
resource intensive.

     One concept is to use the FTP  for conditioning of integrated
refueling/evaporative  emission  control  systems.   Since,  in the
future, the FTP will likely include initial canister breakthrough
loading and a combination of vehicle driving and canister loading
conditions, the test vehicle and fuel vapor  emission control system
would  be conditioned  as they  proceed  through  the  FTP  to  the
refueling measurement test.  Such an approach could eliminate the
need for a special vehicle preconditioning cycle altogether, thus
greatly simplifying the overall test procedure,  except perhaps in
tests run solely for the purpose of assessing compliance with the
refueling emission standard.

     This assessment is based on the FTP sequence proposed in the
evaporative  emissions  workshop  notice  (55 FR 49914,  December 3,
1990);  the  workshop was held  on  December  19,  1990.   Although
currently a proposal,  it represents the best projection of the FTP
likely to be in use at the time the onboard system test procedure
is finalized.   A  diagram of the FTP proposed in  the  workshop is
shown in Figure 2.   It  may be necessary to modify this alternative
if the proposed  FTP  is  substantially  changed  in the  improved
evaporative emissions control rulemaking now underway.

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                  r
     Integrated System
         T" egg •
a. Disconnect Vapor Line to Canister
b. Drain fuel Tank
c. 40?. Fuel ing
d. Reconnect Vapor Line to Canister
e. Drive One LA 4
f. One Hour Hot Soak
g. Repeat  (e) and (C) Twice
h. Disconnect Vapor Line to Canister
i. Drain Fuel Tank
j. 40% Fueling
k. Reconnect Vapor Line to Canister
1. Heat Uuild (60° 4 2°F Initial,
   24 + 1°F Rise)
m. Repeat  (e) Through (1) Twice
n. Drive One LA-4
                                           Can Iste r_Load ing to Breakthrough
                                              0   Drain Fuel Tank
                                              0   Soak Vehicle for  6  Hours
                                              0   Fuel in SHED to Breakthrough
      Integrated System
    ig r Purge,  Coi»tinugus Dr^ve

a. Disconnect Vapor Line to Canister
b. Drain Fuel Tank
c. 403; Fueling
d. Reconnect Vapor Line to Canister
e. Drive Repeated LA-4a Until Mileage
   Accumulated = Mileage Required for
   Purge Equivalent to Cyclic Drive.
   Mileage Accumulation Stops at the
   First Idle Paat the Mileage
   Requirement
       Non-integrated System
Canister Purge, Continuous Drive
 a. Disconnect Vapor Line to Canister
 b. Drain Fuel Tank
 c. 95% Fueling
 d. Reconnect Vapor Line to Canister
 e. Drive Repeated LA-43 Until
    85% of Tank Volume Is
    Consumed
                                                      Vehicle Cool  Down
                                               0 Disconnect Line to Canister
                                               0 Drain Fuel Tank
                                               0 10* Fueling
                                               0 Soak Vehicle 6 to 24 Hours
                                                          I
                                                 Refuel ing Emissions Measurement
                                             Reconnect Vapor Line to Canister
                                             Fuel to Automatic Nozzle Shut-off
                                             (B5* Mimimun Fueling).   Restart Fueling
                                             Following Any Premature Shut-offs Within
                                             15 Secondn)
                                           NPRM Onboard Test  Procedure Flow Chart
                                                                                                       Figure  1

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Proposed Federal Test Procedure
                     Fuel
                9 RVP, 40% full
                      I
                 Preconditioning
                     LA-4
              Purge & Load Canister
            SHED or bench procedure
                      I
                    Refuel
                   Cold Soak
                   68-86° F
                  Exhaust Test
                Fuel Temp Profile
                    Refuel
                                             Refueling Emissions
                                             Measurement Test
                Two Heat Builds
               2 hrs ea, fuel 72-96F
               natural cool to 72° F
                  Diurnal Test
                    2 hours
                  fuel 72-96° F
                    Refuel
                Running Loss Test
              LA-4,2*NYCC,LA-4, 95F
               SHED or point source
                  Hot Soak and
               Permeation Loss Test
                    5 hours
                 ambient 95° F
Refueling Emissions
Measurement Test
                   Figure 2

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                           Refueling Test Procedure:
                                Integrated Systems
                                                               FTP* Through the
                                                                 Exhaust Test
                           Disconnect Refueling Canister
                           Remove Fuel Filler Cap
                           Drain Fuel Tank
                           10% Fueling
                           Replace Fuel Filler Cap
                           Vehicle Temperature Stabilization (80 ± 3°F
                            for at least 6 hours)
                           Connect Refueling Canister
                           Remove Fuel Filler Cap
                           Place Vehicle in Shed
                            Refueling Emissions Measurement Test

              Fuel to Automatic Nozzle Shut-off (85% Minimum Fueling : 81° - 84° F Fuel)
              Restart Fueling Following Any Premature Shut-offs Within 15 Seconds
* The Federal Test Procedure (FTP) refers to the testing sequence that includes exhaust and evaporative
emission system test procedures
                                       Figure 3

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     For integrated  systems,  it  may be appropriate for  the  test
procedure to adopt one of two options which would  use  the FTP to
condition  the  vehicle/canister  for   the  refueling   emissions
measurement test.   The first  option  is shown in Figures 2 and 3 as
the sequence labeled option  "1".  Under this option, the refueling
emissions measurement test would be placed at the  end  of the FTP
and would be retained in the same form as that  described in the
NPRM.

     The basic premise for positioning the refueling test in this
way is that the vapor loads and purge requirements involved in the
evaporative emissions test are expected to be generally sufficient
to test the integrated system's purge capability and to prepare the
system  for  a refueling  event.   Therefore,  a separate refueling
preconditioning would not be needed.

     One possible  issue  concerning use of  the  FTP to condition
vehicles/canisters prior  to  the  refueling test  is the amount of
work that must  be performed if the only objective is conducting the
refueling  measurement test,  such  as  might  occur  for  recall
evaluation  testing  or if the refueling test  were voided during
certification testing by, for example,  the accidental  spillage of
fuel during refueling.  In such instances  the  entire FTP sequence
would  have to  be  performed  for  the purpose  of  conditioning  a
vehicle for a refueling test under Option  1.   It  may be useful to
consider  alternative  methods  of  determining   if  the  vehicle
conditioning sequence can be further abbreviated, while maintaining
proper evaluation of the refueling emission control system.

     Another possible option is the  placement  of the refueling
emissions measurement test after the exhaust emissions measurement
test  in the FTP.    Labeled  option "2"  in  Figures  2 and 3,  this
testing option would provide a shorter preconditioning method for
integrated systems,  and  thus  would  provide a  savings  in time and
resources for those  cases in  which  the  only desired objective is
the  refueling  emissions measurement.    In  this  approach,  the
vehicle/canister  would  be   preconditioned  as  in  the  proposed
evaporative procedure and the vehicle would be driven through the
driving cycles specified  in the exhaust test (exhaust measurements
may or may not be required).  The refueling emissions measurement
test would then be conducted.

     To conduct the evaporative emissions tests under Option 2, the
entire FTP would need be  performed separately.  Alternatively,  it
is possible to  design a  test  procedure  that allows re-entry into
the  FTP sequence  after  completion of the  refueling emissions
measurement test in order to complete the evaporative and running
loss portions of the test.  Use of this approach would require that
additional purge be provided before  continuing through  the  rest of
the FTP, because the refueling event would be expected  to load the
canister to near its  full capacity.  Additional  purge opportunity
could be provided  by inserting  another  exhaust  emissions driving

                                11

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cycle (without measurement),  or some comparable driving sequence,
into the FTP after the refueling emissions test.

     Another approach is to use Option 1 for normal certification
testing, but to retain Option 2  as a stand-alone, short test to be
used at the Administrator's discretion.  This option would provide
maximum flexibility and reduce overall testing resource impacts for
both certification and in-use compliance testing.

2. Preconditioning Non-Integrated Systems

     The   second   test  procedure  modification  which   may  be
appropriate is, again, inspired by the desire to make the onboard
system test less resource-intensive.  Under the August 1987 onboard
proposal,  85 percent  of  the  fuel tank  capacity  must  be consumed
during the preconditioning  sequence for non-integrated systems.  In
the modification being considered, the manufacturers would have the
option  of  using any  integer  number  of continuously  driven LA-4
driving  cycles to  sufficiently condition  the  canister  (by the
manufacturer's definition)  prior to the  refueling test (Figure 4),
provided that  85  percent  or  less of the fuel tank  capacity is
consumed.   This modification would  be  expected to  decrease the
amount  of  testing  resources  required without  lessening  the test
procedure's ability to evaluate the capacity to control refueling
emissions.

     The use of this preconditioning  sequence would be expected to
lead to  similar canister size and purge requirements as the full
drivedown  (85 percent)  option because the manufacturers would still
be required  to pass the refueling emission test.   Consequently,
this revised test sequence might be desirable because it provides
the  opportunity   to   reduce  resource   impacts  for  both  the
manufacturers and EPA. It  should be noted that  the option given in
the  original  proposal to  use test track/road  purge in  lieu of
vehicle dynamometer driving would be retained.

     As  a  possible alternative method for EPA testing  of non-
integrated systems, a vehicle would be fueled to automatic nozzle
shut-off,  driven some integer number  of LA-4 driving cycles, and
then subjected to the  refueling  emissions  measurement test  (Figure
4).  This method differs from the above-described modification in
that the SHED  refueling  event would  directly follow the driving,
with no  intervening drain  and fill to 10  percent,  and in that it
would be conducted  at EPA's  discretion  only.   The  basis for this
approach is the fact that partial refuelings are common in use and
so  an  onboard system should  have  adequate   design margin  to
accommodate partial refuelings.   The number of LA-4s driven would
be at EPA's discretion on a per test basis.
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                          Refueling Test  Procedure:
                            Non-Integrated  Systems
                                    Canister Loading
                           Drain Fuel Tank
                           Soak Vehicle for at Least 6 Hours at 80° ± 3° F
                           Load Canister(s) to Breakthrough
                           (Identical to Evap Loading Technique)
     Continuous Drive Canister Purge

  • Disconnect Vapor Line to Canister
  • Drain Fuel Tank
  • 95% Fueling: 81° - 84° F Fuel
  • Reconnect Vapor  Line to Canister
  • Drive the Number of LA-4s Specified by
    Manufacturers (up to 85% of Fuel Tank)
• Disconnect Vapor Line to Canister
• Drain Fuel Tank
•10% Fueling
• Soak Vehicle for at Least 6 Hours at 80° ± 3° F
• Reconnect Vapor Line to Canister
• Remove Fuel Filler Cap
• Place Vehicle in Shed
   Refueling Emissions Measurement Test
 > Fuel to Automatic Nozzle Shut-off
   (85% Minimum Fueling : 81° - 84° F Fuel)
 • Restart Fueling Following Any Premature
  Shut-offs Within 15 Seconds
        Testing Option for EPA
• Disconnect Vapor Line to Canister
• Fuel to Automatic Nozzle Shut-off
 (at Least 95% of Fuel Tank, 81-84 F Fuel)
• Reconnect Vapor Line to Canister
• Drive Integer Number of LA-4s Determined
 by EPA
• Remove Fuel Filler Cap
• Place Vehicle in Shed
  Refueling Emissions Measurement Test

 Fuel to Automatic Nozzle Shut-off
 (at least as much fuel as used during drive,
 81 °-84° F Fuel)
 Restart Fueling Following Any Premature
 Shut-offs Within 15 Seconds
                                         Figure 4

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                                                                       P.16
     The refueling emissions measurement test contains a provision
for fueling to automatic shut-off, and,  because automatic shutoff
is commonly practiced in use (even for small partial fills such as
with rental car returns), it would appear reasonable to retain this
provision for this test  as  well.   However,  the automatic shutoff
mechanisms on fuel pumps  are not designed to  ensure that a measured
volume of fuel is in  the vehicle  fuel tank at shutoff.  Therefore,
it is likely that the refueling measurement test would add somewhat
more or less fuel than was burned during the LA-4 driving cycles,
thus introducing uncertainty into the results.  The effect of this
variability in nozzle shutoff on a test involving just a few LA-4
cycles of drivedown could be significant.

     Concern about pumping too much fuel would tend to be mitigated
by the fact that  the  rate of hydrocarbon reduction during purge is
generally much higher when the  canister  is heavily  loaded with
hydrocarbons  (i.e. during the  initial LA-4  cycles)  than when the
hydrocarbon concentration in the  canister has  been  reduced, thus
helping to ensure that the purge provided by initial drivedown of
a  fully  loaded canister  will  free up  more than enough storage
capacity to accommodate the corresponding partial refueling vapor
load.  EPA would welcome  input  from others  on  whether or not the
higher purge  rates present at the  start  of a purge  cycle would
adequately cover for nozzle shutoff uncertainties.

     To avoid inaccurate test  results caused by the pumping of too
little fuel,  the  test  procedure would need  to ensure  that the
amount of fuel dispensed during the refueling measurement test is
at least as much  as that burned during the LA-4  driving.  To verify
this, some method of determining the amount of fuel consumed during
the  driving  sequence would  need to  be  included,   such  as  by
measuring exhaust emissions during some portion of the driving and
performing a carbon balance calculation, or  by  using the vehicle's
previously  determined fuel economy rating.   The amount  of fuel
pumped during the  refueling test would also need to be metered to
ensure that,  if  automatic pump  shut-off were to occur before the
proper amount  of fuel was displaced,  refueling  would be resumed
until  sufficient  fuel  was  pumped.    EPA   would  welcome  other
suggestions for dealing for pump shutoff variability.

     One of the more attractive features of a non-integrated system
(fully separate  refueling  and evaporative  systems)  is  that  it
permits a lower purge rate than for an integrated system since the
purge of the refueling canister can be spread more evenly over the
driving associated with the fuel dispensed.   This lower purge rate
is  valuable since  it allows  for a reduction  in the  potential
effects   of   purge  on  exhaust   emissions.     Considering  the
sophisticated purge strategies available with electronic controls,
there  is  some concern  that,  because of potential  purge/exhaust
emission  interactions,  manufacturers could  design  a purge system
which  operates at lower purge rates during the exhaust emission
test  than  during  a  subsequent portion  of the preconditioning

                                14

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                                                                       P.17
driving  cycle.     To  avoid  the  possibility   of   adverse  or
unrepresentative exhaust emission effects, it may be necessary to
include  a  requirement  that,  for  vehicles using non-integrated
systems, the purge volume must be essentially the  same  for each LA-
4 driving cycle during the test.

     Finally,  it  may be appropriate  to apply the procedure for
loading  canisters to  breakthrough proposed  in   the  evaporative
emissions revisions to the FTP  (55 FR 49914, January 19,  1990) to
tests  of non-integrated systems  as  well as  integrated  systems.
This would  simplify testing procedures  and reduce the  need for
additional  equipment.    Any  subsequent  changes  to   the  loading
procedure resulting from finalization of the improved evaporative
rule would be factored in as well.

3. Testing of Seals and Connections

     Vapor emissions from a refueling emissions test can occur from
two sources: emissions vented from the canister and emissions that
escape  from the fillpipe seal,  vapor  line connections,  and other
leaks.   The test  procedures proposed  in the NPRM and the options
described  above test  for  both  of these  sources of emissions.
Although the purge/canister system capacity  and operation would be
evaluated through the full preconditioning and refueling emissions
measurement  sequence,  there  may be  situations   in  which  it is
desirable to only measure emissions arising from areas other than
the canister.

     Therefore, it  may be  appropriate to  add a test  procedure
option, to be used at EPA's  discretion only, in which the canister
would be thoroughly bench purged prior  to conducting a refueling
emissions measurement test.  The canister would then be reconnected
and the normal refueling emissions measurement test conducted.  The
emissions would need to meet the  refueling emission  standard in
order to pass the test.  The advantage of this type of test over a
complete test sequence is  that the  integrity  of the seals and
connections can be  determined with a modicum of  effort  in cases
where this determination is the only desired result.

4. Lower Limit on Refueling Dispensing Rate

     In its proposal, EPA had specified a fuel dispensing rate of
approximately 10 gallons per minute (gal/min) for  refueling tests.
An option  was included,  however,  for EPA to test at lower flow
rates if desired.   This was  done to  ensure that  the Agency would
have the ability to  adequately test systems which  it believed might
lose control effectiveness  at low flow rates.  Based upon comments
received, it may be appropriate to specify a lower limit for such
testing.    Since  extremely  low  dispensing rates would not  be
expected  to  occur  in  use,  they  would  be  unrepresentative.
Consequently,  replacing the  10  gal/min  proposed rate with  a
dispensing rate range of 4-10 gal/min may be a reasonable solution.

                                15

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                                                                        P.18
Nearly  all  in-use refuelings  occur at  a rate  of 5  gal/min  or
greater, and at least some  fuel dispensing nozzles themselves fail
to operate properly if used at 3 gal/min.

II. Impact of Changed Circumstances on the Proposed Action

     In addition to the impacts on the test procedure discussed in
Section I.G, the  changed circumstances  discussed in Section I  of
this document have potential  impacts on costs, benefits (emissions
reductions),  and  the  resulting  cost  effectiveness   of  onboard
controls.

     A  revised cost  analysis,   addressing  most  of the  changed
circumstances discussed in  Section I of this document, is contained
in an EPA memorandum,  dated December 22,  1988, available in Public
Docket No. A-89-18, item II-B-6.  This analysis calculated onboard
control costs based on a design incremental to improved evaporative
controls,  a simplified onboard system design concept,  and 9.0 psi
RVP certification fuel.  The resulting estimated cost increment was
lower than the NPRM estimate.  An adjustment for the fuel recovery
credit provided by combustion of the collected vapors resulted in
a net average  cost savings of a few dollars per vehicle.   Since
there are  Stage II vapor  recovery  systems  in some areas  of the
country now,  and  their use is expected to expand  to  a number  of
other areas under the CAAA  of 1990, it is worthwhile assessing the
affects of Stage II on EPA's  cost analysis for an onboard equipped
vehicle.   Based  on  current  onboard  and Stage  II technologies,
refueling events in nonattainment areas in which both onboard and
Stage II systems are operative will result in the refueling vapors
being  captured by the  onboard system;  thus the onboard fuel
recovery credit would be retained.  Without this adjustment for the
fuel recovery  credit it is expected that,  instead of a small per
vehicle net cost savings, a positive average cost of a  few dollars
per vehicle would result.

     The  changed  circumstances  discussed in  Section  I  of this
document will produce a small net decrease in emissions reduction
benefits of onboard controls, compared to the benefits calculated
in the NPRM.  The effect of volatility controls was accounted for
in the sensitivity analysis in Section V of the NPRM, yielding the
conclusion  that the annual  average gasoline  refueling  emission
factor is about 11 percent less  for the case in  which summertime
RVP is  controlled in class C areas  at  9.0 psi  than  the  case  in
which it  is set  at  11.5 psi.    It  is also possible that  use  of
reformulated gasoline  in  some nonattainment areas  would  cause a
slight reduction in benefits.

     The  implementation  schedule  for  onboard  controls  would
obviously impact  how quickly  emissions  reductions would begin to
occur.  However,  it  is  reasonable  to  expect  that the full annual
benefit would eventually be attained as phase-in and fleet turnover
progresses.  The installation of Stage II systems,  required in some

                                16

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                                                                       P.19
nonattainment areas by the 1990 CAAA,  would also temporarily reduce
the emissions control benefit of onboard systems.  However, because
the Act  also calls for the retirement  of the federally-mandated
Stage  II  control  requirements   once   onboard  controls  are  in
widespread use,  the reduction  in  onboard control benefits would be
expected to  be  temporary.   It should  be noted that  the onboard
control standards and their implementation schedule  are intended to
apply to vehicles sold in all parts of the  United  States,  even
where Stage  II  controls are  (or will  be)  in place,  such  as in
California.

     Because, as discussed above, the net cost  of onboard refueling
emissions control is projected to be  modest, the impact of changed
circumstances on  calculated benefits  does  not alter the NPRM's
general conclusion regarding cost-effectiveness.
                                17

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