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OAR Box 1818 

Prepped by Ollie Stewart 

Document Number: 

76) IV-A-5 

Docket Number: 

A-87-11 

Printed 11/6/2008 3:12:46 PM Sheet 76 of 79 
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/A-87-11 

w- A - 5 

Summary of Changed Circumstances 

Control of Air Pollution From New Motor Vehicles and New Motor 

Vehicle Engines; Refueling Emission Regulations for GasolineFueled 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 
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 A T - 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. 

A T = (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 lbs. loaded vehicle weight and 6,000 lbs. 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 phasein 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. 
J: 

Integrated System 

€jDigkgF-J>"

rge» Cyclic Drive 

Disconnect Vapor Line to Canister 

Drain Fuel Tank 

40* Fueling 

Reconnect Vapor Line to Canister 

Drive One LA-4 

f. One Hour Hot Soak 

g. Repeat (e) and (f) Twice 

li. Disconnect Vapor Line to Canister 

i. Drain Fuel Tank 

j. 40% Fueling 

k. Reconnect Vapor Line to Canister 

1. Heat Build (60° + 2°F Initial, 

24 + 1°F Rise) 

m. Repeat (e) Through (1) Twice 

n. Drive One LA-4 

Canister Loading to Breakthrough 

° Drain Fuel Tank 

° Soak Vehicle for 6 Hours 

" Fuel in SUED to Breakthrough 

Integrated System 

Canister Purge. Continuous Drive 

a. Disconnect Vapor Line to Canister 

b. Drain Fuel Tank 

c. 403; Fueling 

d. Reconnect Vapor Line to Canister 

e. Drive Repeated LA-4s Until Mileage 

Accumulated = Mileage Required for 

Purge Eguivalent to Cyclic Drive. 

Mileage Accumulation Stops at the 

First Idle Past the Mileage 

Requirement 

Vehic 

° Disconnect 

le Cool Down 

Line to Canister 

° Drain Fuel Tank 

° 10* Fueling 

° Soak Vehicle 6 to 24 Hours 

1 

X 

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-4s Until 

85* of Tank Volume Is 

Consumed 

Refueling Emissions Measurement 

Reconnect Vapor Line to Canister 

Fuel to Automatic Nozzle Shut-off 

(85* Mimimun Fueling). Restart Fueling 

Following Any Premature Shut-offs Within 

15 Seconds) 

NPR M Onboard Test Procedure Flow Chart 

Figure 
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Proposed Federal Test Procedure 

Fuel 

9 RVP, 40% full 

I Preconditioning 

LA-4 

I 

Purge & Load Canister 

SHED or bench procedure 

Refuel 

Cold Soak 

68-86° F 

—r~ 

Exhaust Test 

Fuel Temp Profile 

ZE7 

Refuel 

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 

© 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 

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P.14 

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 nonintegrated 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. 

12 
P.15 

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) 

I 

Continuous Drive Canister Purqe 

• 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 

1 

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 l_A-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 
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 
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 LA4 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. 

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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 

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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. 

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