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OAR Box 1818 

Prepped by Ollie Stewart 

Document Number: 

65) ll-F-6 

Docket Number: 

A-87-11 

Printed 11/6/2008 3:12:46 PM Sheet 65 of 79 
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A - ffi.- M in-*-*«•» 

6560-26 

ENVIRONMENTAL PROTECTION AGENCY 

40 CFR Part 86 

[AMS-FRL- ] 

Control of Air Pollution from New Motor 

Vehicles and New Motor Vehicle Engines: 

Refueling Emission Regulations for 

Gasoline-Fueled Light-Duty Vehicles, 

Light-Duty Trucks, and Heavy-Duty Vehicles 

AGENCY: Environmental Protection Agency (EPA). 

ACTION: Notice of Proposed Rulemaking. 

SUMMARY: This notice contains EPA's proposed regulatory 

requirements for a vehicle-based program to control 

refueling emissions from gasoline-fueled light-duty 

vehicles, light-duty trucks, and heavy-duty vehicles. The 

proposed standard is 0.10 grams of vapor per gallon (g/gal) 

of dispensed fuel. For light-duty vehicles and light-duty 

trucks, a 0.10 g/gal standard is also proposed for 

high-altitude conditions. The proposed test procedure for 

determining compliance with the standard uses the Sealed 

Housing for Evaporative Determination (SHED) in a way 

similar to that currently used for testing evaporative 

hydrocarbon emissions. The year of implementation is 

proposed to be two or more model years after promulgation 

of the final rule. 
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The Agency believes that the proposed control of 

refueling emissions is warranted for a number of reasons. 

It can improve ambient ozone levels in all areas of the 

country including those that are currently, or are 

projected to be, in violation of the National Ambient Air 

Quality Standard for this pollutant. Also, the' proposed 

vehicle-based control program will provide important 

ozone-related benefits in areas that are now in compliance 

with the ambient standard. Further, the proposed emission 

controls will help protect the general public from the 

risks of cancer due to exposure to benzene, a component of 

gasoline vapor, and to evaporated gasoline as a whole. 

This proposal would reduce emissions of gasoline refueling 

vapors by nearly 90 percent from uncontrolled levels. 

In another part of today's Federal Register, the 

Agency is proposing to regulate the volatility of 

commercial gasoline. Due to the interactions between that 

rulemaking and this action on refueling emissions, the 

Agency suggests the interested reader consult both notices 

for a better understanding of today's proposals. 

DATES: EPA will conduct a three-day public hearing on this 

Notice of Proposed Rulemaking and on the gasoline 

volatility proposal approximately 60 days after Federal 

Register publication. The specific dates of the hearing 

will be announced in a subsequent Federal Register notice. 

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Comments on this proposal will be accepted for 30 days 

following the conclusion of the hearing. Additional 

information on the public hearing and the submission of 

comments can be found under "Public Participation" in the 

Supplementary Information section of today's notice. 

ADDRESSES: The public hearing will be held in Washington, 

DC. The exact location will be announced in a subsequent 

Federal Register notice. 

Interested parties may submit written comments (in 

duplicate if possible) to Public Docket No. A-87-n, at: 

Central Docket Section (A-130) 

U.S. Environmental Protection Agency 

Attention: Docket No. A-87-11 

401 M Street, SW 

Washington, DC 20460 

Materials relevant to this proposed rulemaking have 

been placed in Docket No. A-87-11 by EPA. Public Docket No. 

A-84-07, established in support of EPA's assessment of air 

pollution regulatory strategies for the gasoline marketing 

industry, also contains considerable background information 

and has been incorporated by reference into A-86-11. The 

dockets are located at the above address in the West Tower 

Lobby, Gallery I, and may be inspected between 8 a.m. and 4 

p.m. Monday through Friday. A reasonable fee may be 

charged by EPA for copying docket materials. 

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FOR FURTHER INFORMATION CONTACT: 

Mr. Richard S. Wilcox 

Standards Development and Support Branch 

Emission Control Technology Division 

U.S. Environmental Protection Agency 

2565 Plymouth Road 

Ann Arbor, MI 48105 

Telephone: (313) 668-4390 

SUPPLEMENTARY INFORMATION: 

I. Background 

A. Introduction 

Questions regarding the need for control of refueling 

emissions from gasoline-fueled vehicles and how such 

control should be obtained have stimulated considerable 

interest. To facilitate an understanding of the complexity 

of the issues surrounding the control of refueling 

emissions, a short review of the history of this subject is 

presented in the remainder of this section (Section I), 

including a brief overview of the environmental issues 

which have led to present concerns about these emissions. 

Following that background information, Section II more 

fully describes and quantifies the environmental effects 

associated with refueling emissions in terms of ambient air 

quality (ozone), the human cancer risks due to direct 

personal exposure, the need for control of these emissions, 

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and the decisionmaking process that has led to EPA's 

conclusion that requiring vehicle-based vapor recovery, or 

onboard systems,* is the preferred control approach. 

Section IV discusses potential challenges to EPA's legal 

authority for implementing onboard rather than Stage II 

refueling controls. 

Elsewhere in today's Federal Register, EPA is 

proposing to reduce the volatility of in-use gasoline from 

current levels. This action will control excessive 

evaporative emissions from the motor vehicle fleet and also 

reduce evaporative VOC from certain stationary sources 

(i.e., storage tanks). However, the analyses contained in 

this refueling proposal were performed under the assumption 

that onboard control systems would be certified with fuels 

representing current summertime commercial fuels (i.e., 

with certification fuel having a Reid Vapor Pressure (RVP) 

of 11.5 pounds per square inch). This situation represents 

the most difficult case in terms of motor vehicle 

manufacturer compliance and also indicates the Agency's 

intent to adopt onboard controls regardless of what 

decision is eventually made with respect to fuel 

volatility. The effect of volatility control as it regards 

the decision to control refueling vapors will be highlighted 

Onboard vapor recovery controls are self-contained 

systems located entirely within the vehicle. See 

Section II.D. of this notice. 

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at appropriate points in this notice. The effect of fuel 

volatility on the benefits, cost, and cost effectiveness of 

refueling control is also separately discussed in Section V. 

The last section of this preamble (Section VI) 

presents a complete description of today's proposal and 

other relevant information. This includes the derivation 

of the proposed standard, a review of the proposed test 

procedure and its integration with the existing testprotocols, leadtime, enforcement protocols,, safety and 

economic impacts. Section VI also describes several 

proposed test procedure changes that are related to 

evaporative emissions control. They are being proposed 

primarily to ensure that evaporative emissions are 

appropriately measured in determining compliance with 

emission standards and to clarify the definition of 

evaporative emissions. The revisions are intended to 

parallel the same proposed changes included in EPA's 

proposal to regulate fuel volatility, which appears 

elsewhere in today's Federal Register. While they are 

described further later in this refueling proposal, the 

principal rationale for these changes is found in the fuel 

volatility proposal. 

Finally, it should be noted that the cost and benefit 

analyses which are described in today's proposal were based 

on the assumptions that Stage II controls would begin to be 

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implemented as early as mid-1988 or as late as 1990, 

depending on the control scenario, and that onboard 

controls would be implemented beginning with the 1990 model 

year. Depending on the time required to complete this 

rulemaking, different effective dates than these could be 

promulgated. However, this fact does not significantly 

affect the decision to propose an onboard vapor recovery 

standard, because the costs and benefits of the two control 

technologies are essentially unaffected and the relative 

ranking of the alternatives is unchanged by the exact 

effective dates ultimately chosen. (More detailed 

descriptions of the potential leadtime requirements and the 

effective date of the standard are presented in the safety 

and leadtime discussions found in Section V.) 

B. History of Refueling Controls 

The contribution of hydrocarbon emissions from 

gasoline refueling operations to ambient ozone levels has 

been of concern for some time.* This concern led EPA to 

promulgate regulations under Section 110(c) of the Clean 

Air Act (CAA) in the mid-1970s that would have required the 

installation of gasoline vapor recovery systems at service 

stations, or Stage II systems,** in all or part of eleven 

* Diesel refueling operations have not been a concern 

due to the low volatility and, hence, low emissions 

potential of diesel fuel relative to gasoline. 

** Stage II vapor recovery systems are integrated with 

the fuel dispensing equipment. See Section II.D. 

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Air Quality Control Regions (AQCRs) in eight states [e.g., 

38 FR 30524 (November 7, 1973), 39 FR 4881 (February 8, 

1974), and 39 FR 21053 (June 18, 1974)]. The Agency 

proposed amendments to those regulations in October 1975 

(40 FR 47668) and, based on the comments received and 

information developed during that rulemaking, new 

regulations were proposed in November 1976 (41 FR 48043). 

On May 31, 1977, EPA deferred until further notice the 

required Stage II compliance dates for these eleven AQCRs 

(42 FR 27674). Action on the proposed revisions to the 

earlier Stage II regulations was never completed, nor were 

the previous compliance dates reinstated. Also, in August 

1977 the CAA was amended to add several specific provisions 

pertaining to the control of refueling emissions. 

Section 202(a)(6) of the CAA, added in 1977, directs 

the Administrator of EPA to "determine the feasibility and 

desirability of requiring new motor vehicles to utilize 

onboard hydrocarbon control technology which would avoid 

the necessity of gasoline vapor recovery of uncontrolled 

emissions emanating from the refueling of motor vehicles." 

This section further provides, that, "[if] the 

Administrator finds that it is feasible and desirable to 

employ such technology, he shall...prescribe, by 

regulation, standards requiring the use of onboard 

hydrocarbon technology...." In response to this statutory 

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requirement, . EPA undertook a review and analysis of 

available information in the late-1970's, and tentatively 

determined that onboard control for light-duty vehicles was 

technically feasible.[1] 

However, in light of the serious financial 

difficulties faced by the automotive industry in 1980 and 

1981, EPA conducted a review of its regulatory programs to 

identify possible changes that could reduce the regulatory 

burden on the industry. As a result of that review, EPA 

decided in 1981 that the use of onboard technology for the 

control of refueling emissions was undesirable at that 

time. Thus, the Agency announced that onboard controls 

were not being required (46 FR 21629, April 13, 1981). Now 

that the economic crisis within the automotive industry has 

passed, and in light of new information concerning the need 

for ozone reduction measures and the potential adverse 

health effects from inhaling gasoline vapors, EPA is 

reevaluating possible action under Section 202 (a)(6) of 

the CAA. 

Although no onboard standard or revised final 

regulations for Stage II controls have been promulgated by 

EPA, refueling emission control has been achieved in 

limited geographical areas of the country. Stage II 

control systems are being used in 26 counties of California 

and in the District of Columbia as a means of improving 

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ozone air quality. These requirements have been in effect 

since the mid-1970s, and have demonstrated the feasibility 

of Stage II controls. 

In addition, EPA and certain states continue to view 

the control of refueling emissions as a desirable ozone 

reduction strategy. For example, several states committed 

in their 1982 ozone state implementation plans (SIPs) to 

consider Stage II regulations. These states were among a 

number of states that, as of February 1983, contained ozone 

non-attainment areas and had been granted extensions by EPA 

beyond the statutory attainment date of December 31, 1982, 

as provided for under Section 110 of the CAA. Further, 

resolutions were passed in 1982 and again in 1985 by both 

the State and Territorial Air Pollution Program 

Administrators (STAPPA) and the Association of Local Air 

Pollution Control Officials (ALAPCO). These resolutions 

requested that EPA review Stage II control technology and 

publish a control techniques guideline document for use by 

the various state air pollution control agencies that would 

define Stage II controls as "reasonably available control 

technology" under Section 172 of the CAA. Such an action 

would have the effect of promoting the use of such controls 

in ozone non-attainment areas. Similar resolutions were 

also passed in 1986, and included the request that EPA 

promulgate onboard control requirements as a long-term 

emission reduction strategy. 

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The relationship between refueling emissions and ozone 

air quality has been . carefully considered by EPA ozone 

experts. As described more fully later in today's notice, 

the ozone attainment problem facing the nation is now 

extremely serious, and its solution will require a 

well-coordinated, aggressive effort aimed at bringing all 

areas of the country into compliance with the ozone NAAQS. 

This effort will include a mixture of state and Federal 

actions. Among the potential Federal actions that EPA has 

considered as possible nationwide emission control measures 

is the reduction of refueling emissions through the use of 

onboard or Stage II technology. EPA anticipates publishing 

a proposed comprehensive ozone strategy in the near future 

and refueling controls almost certainly will play a 

significant role in that strategy. 

While the link between refueling emissions and ozone 

formation has been recognized for some time, there is also 

evidence that exposure to gasoline vapor resulting from 

refueling emissions poses direct risks to public health. 

Gasoline and its vapors are a complex mixture of volatile 

organic compounds (VOC). One of the most important 

constituents in gasoline, from a public health effects 

perspective, is benzene. Epidemiological studies strongly 

suggest that benzene is a human carcinogen. Also, 

laboratory studies have shown this compound to cause 

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multiple cancers in animals. Based on this evidence, 

benzene was listed by the Agency in June 19 77 as a 

hazardous air pollutant under Section 112 of the Act (42 FR 

29332). 

(Additional information regarding EPA's decision to list 

benzene as a hazardous air pollutant can be found in Docket 

Number OAQPS-79-3 (Part I).) 

More recently, carcinogenic concerns with refueling 

emissions have focused not just on benzene, but gasoline 

vapors in general. Laboratory tests conducted by the 

American Petroleum Institute (API) have shown wholly 

vaporized gasoline causes cancer in animals. The API and 

other studies were independently reviewed by EPA's Science 

Advisory Board (SAB) and by the Health Effects Institute 

(HEI).* After carefully considering the available 

evidence, EPA has concluded that gasoline vapors are a 

probable human carcinogen under EPA's Cancer Risk 

Assessment Guidelines (51 FR 33992, September 24, 1986). 

The SAB is a group of experts from various scientific 

organizations that advises the Administrator on the 

scientific validity and usefulness of information 

developed in support of regulatory activities. HEI is 

a non-profit research organization established and 

sponsored jointly by EPA and the automotive industry 

to provide and evaluate data on the health effects of 

emissions from motor vehicles. 

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This conclusion is shared by SAB and HEI. The basis of 

EPA's decision and accompanying risk estimates are 

discussed further in Section II.C. of today's notice. 

C. EPA's Study of Refueling Emissions 

On August 8, 1984, EPA announced the public 

availability of an extensive analysis of the gasoline 

marketing industry (49 FR 31706). This draft study,* 

"Evaluation of Air Pollution Regulatory Strategies for 

Gasoline Marketing Industry,"[2] (hereafter referred to as 

"the draft gasoline marketing study") was prepared by EPA's 

Office of Air Quality Planning and Standards and the Office 

of Mobile Sources. The analyses included in that document 

quantified the emissions and health risks associated with 

all components of the gasoline distribution and marketing 

network, from the delivery of gasoline from refineries, to 

the refueling of vehicles at service stations. The 

analyses also estimated the costs, emission reductions, 

risk reductions, and economic impacts associated with the 

many control strategies considered. Implicit in this draft 

study was EPA's desire to reevaluate the 1981 decision not 

to require onboard controls. 

In making the draft gasoline marketing study publicly 

available, EPA solicited comment. on the document's 

methodology, assumptions, and conclusions. At that time, 

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EPA stated that all such comments would be considered in 

determining the need for and nature of any regulatory 

strategies for this industry. Over 180 written comments 

from individuals, state and local governments, and industry 

were received. The submissions ranged from one-page 

letters to detailed analytical documents consisting of 

hundreds of pages from such industry groups as the American 

Petroleum Institute (API) and the Motor Vehicle 

Manufacturers Association (MVMA). The comments were broad 

in scope, covering all aspects of the Agency's analyses. 

As a result of the comments and the availability of 

new or updated information, the Agency undertook a thorough 

and lengthy review of the gasoline marketing study. This 

effort has culminated in a revised analysis. Based on the 

contents of this final study and other supporting analyses, 

which are contained in the draft Regulatory Impact Analysis 

(RIA),[3] EPA believes that the control of vehicle 

refueling emissions is appropriate, and that onboard 

controls are feasible and desirable. Thus, EPA proposes to 

require onboard controls. 

The following sections review key findings of EPA's 

analyses and present the decision rationale that supports 

today's proposal. Readers wishing to obtain more detailed 

technical information should consult the draft RIA, which 

is available in the public docket for inspection. 

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II. Environmental Concerns and Evaluation of Control 

Strategies 

A. Introduction 

This section quantifies the environmental effects 

associated with refueling vapors and describes the need for 

control of these emissions. It also contains an overview 

of the alternative refueling emission control technologies, 

and presents the Agency's rationale for choosing onboard 

vapor recovery systems as the most desirable and 

appropriate means of addressing the environmental 

concerns. As a prelude to these discussions, the next 

section presents a brief characterization of the emissions 

associated with the refueling process. 

B. Sources and Composition of Refueling Emissions 

About 90 percent of all refueling emissions consist of 

vapors displaced from the vehicle fuel tank by the incoming 

gasoline. The mass of these emissions depends on the 

volume of vapor displaced and its density, which in turn 

are determined by the temperature of the fuel being 

dispensed and of that already in the tank, the tank size 

and geometry, the volatility of the fuel, and a number of 

other minor factors. (The determinants of mass refueling 

emissions are discussed in greater detail in "Refueling 

Emissions from Uncontrolled Vehicles,"[4] an EPA technical 

report available for review in the public docket.) 

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Less significant sources of refueling emissions are 

spillage and underground tank emptying losses. Spillage 

occurs as a result of "splash back" from the fill pipe or 

the escape of gasoline from the dispensing nozzle. 

Underground tank emptying losses represent the escape of 

vapor from the vent of the service station underground 

storage tank. This emptying loss occurs because as fuel is 

pumped into the vehicle fuel tank, ambient air is ingested 

into the service station tank through its tank vent. This 

"fresh" air causes liquid fuel to evaporate, in the tank 

until an equilibrium concentration between the vapor and 

liquid phases is reestablished. As this process occurs, 

the pressure within the tank may temporarily become greater 

than the atmospheric pressure. The excess pressure within 

the underground tank is relieved when a small volume of 

gasoline vapor is emitted from the vent. The spillage and 

emptying loss sources each account for about 5 percent of 

the total emissions associated with the refueling 

process.[3] 

The composition of refueling vapors depends on their 

source (e.g., fuel tank displacement or spillage), the fuel 

type (e.g., leaded or unleaded), and the volatility of the 

fuel. Gasoline, in general, is a complex mixture 

containing varying amounts of hydrocarbons belonging to 

four main groups, and much smaller amounts of various 

additives. The hydrocarbons in gasoline are classified as 

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paraffins (alkanes), olefins (alkenes), naphthenes 

(cycloparaffins or cyclanes), and aromatics (benzene or 

benzene derivatives). Gasoline also contains certain 

additives, which are generally present in very limited 

amounts, to provide specific product qualities. 

The composition of the liquid gasoline and that of its 

vapor are not necessarily the same. For example, the 

largest source of refueling emissions, that portion 

resulting from vapor displacement in the vehicle fuel tank, 

does not consist of fully volatilized gasoline. All 

available information shows that the "light-end" 

hydrocarbons generally evaporate more readily than the 

higher molecular weight hydrocarbons, and so refueling 

emissions are primarily light-end hydrocarbons. In 

general, data show that 70 percent or more of the emissions 

by mass are comprised of hydrocarbon molecules containing 5 

or fewer carbon atoms (e.g., butanes and pentanes). 

Further, data show that paraffins (alkanes) are the largest 

constituent among the other major hydrocarbon groups in 

refueling emissions. 

The portion of refueling emissions that results from 

spilling gasoline, on the other hand, reflects the 

composition of the liquid fuel. This is due to the total 

evaporation of liquid fuel that is spilled. However, as 

rioted above, EPA estimates that no more than 5 percent of 

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total refueling emissions currently result from fuel 

spillage and evaporation. Thus, the statements made with 

respect to the composition of refueling emissions due to 

vapor displacement are essentially valid for total 

refueling emissions as well. 

While the majority of refueling emissions are the 

light-end hydrocarbons, the other components of liquid 

gasoline are also represented in the vapor emissions 

generated during the refueling event. Benzene is of 

particular concern to EPA, as previously noted. A recent 

EPA study suggests that under average conditions, a liquid 

fuel containing 1.6 weight percent benzene would generate 

refueling vapors containing 0.8 weight percent benzene.[5] 

C. Environmental Need for Control 

The principal environmental concerns associated with 

refueling emissions focus on their contribution to ozone 

formation in the atmosphere and on their direct health 

effects. Each of these areas is discussed separately below. 

1. Refueling Emissions as an Ozone Precursor 

As noted above, refueling emissions consist almost 

entirely of hydrocarbons. In the presence of sunlight, 

these volatile organic compounds (VOC) combine with other 

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pollutants, in a series of chemical reactions, to produce 

ozone (and other photochemical oxidants). The myriad of 

adverse effects that may result from exposure to ozone, are 

thoroughly described elsewhere and are not repeated in 

detail here.[6] In summary, ozone and other oxidants are 

pulmonary irritants that adversely affect pulmonary 

membranes, lung tissues, and lung function. Animal studies 

also indicate that ' ozone may lead to an increased 

susceptibility to bacterial infection. These detrimental 

health effects may aggravate existing illness or lead to an 

lung disease. In addition to human health concerns, ozone 

may adversely affect vegetation and cause damage to various 

types of materials (e.g., elastic compounds). 

In accordance with Section 109 of the CAA, EPA 

promulgated and revised primary and secondary National 

Ambient Air Quality Standards (NAAQS) for ozone in the 

1970's. The primary standard is intended to protect the 

public health with an adequate margin of safety.* The 

secondary standard is aimed at protecting the public 

welfare. The current NAAQS (i.e., both primary and 

secondary) for ozone requires that the expected number of 

days in a calendar year with one-hour measured 

The current primary standard is principally based on 

well documented studies of acute health effects. 

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concentrations above 0.12 parts per million (ppm) be less 

than or equal to one. 

Section 172 of the CAA generally required all states 

to submit State Implementation Plans (SIPs) that provided 

for attainment of the national primary standard by December 

31, 1982. This deadline was extended to December 31, 1987 

for states that showed attainment by 1982 to be impossible 

despite the application of all reasonably available control 

measures. The SIPs for these "extension" areas were to 

include certain specific measures (e.g., vehicle inspection 

and maintenance programs) and, like the SIPs for areas with 

a 1982 attainment date, were to contain stationary source 

emission controls reflecting reasonably available control 

technology. Also, this section of the statute mandates 

that SIPs provide for attainment of the national secondary 

standard as expeditiously as practicable. 

Section 109(d) of the CAA requires EPA to periodically 

reassess each NAAQS, including the ozone standards, to 

ensure that the public health and welfare continues to be 

protected within the statutory guidelines. Based on the 

results of such reviews, including an independent 

assessment by the Clean Air Scientific Advisory Committee 

(CASAC), EPA may revise the applicable ambient air quality 

standards as appropriate. In the last several years, EPA 

a"nd numerous independent research organizations launched a 

massive effort to better understand and quantify the 

environmental effects of ozone air pollution. The NAAQS 

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for ozone is currently being reassessed by the Agency and 

CASAC in light of resulting health and welfare effects 

research. 

Non-Attainment Areas. Despite the imposition of 

various HC controls, many areas of the nation continue to 

violate the ozone NAAQS. Based on the latest three-year 

period for which complete air quality monitoring data are 

available (1982-84), EPA has determined that more than 70 

urban areas are currently exceeding the ambient standard. 

Twelve of these areas are located in California. The 

significance of the nationwide non-attainment problem is 

clearly indicated by considering the fact that well over 

100 million people live in the areas which are known to 

exceed the ozone standards. 

In addition to reviewing the present state of ozone 

air quality, EPA has also assessed the need for additional 

future hydrocarbon control by making projections of future 

air quality trends. For this rulemaking, estimates of 

future air quality were made for 61 non-California urban 

areas that are currently in non-attainment status.* 

California areas were excluded from the modeling 

projections because that state already controls refueling 

emissions with Stage II vapor recovery systems in 

non-attainment areas. Current attainment areas were also 

This represents the estimated number of non-attainment 

areas at the time this analysis was performed. 

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excluded from the analysis, although it should be noted 

that a number of these areas are very close to the 

standard. If these areas had been included in EPA's 

analysis, it is possible that some of them would have been 

projected to become non-attainment areas in the future due 

to the effects of growth. Thus, the total number of 

non-attainment areas in the future may be greater than 

shown below. 

As with any projection of future events, air quality 

models rely on a variety of assumptions regarding such 

things as emission rates, growth rates, control 

technologies, emission standards, and control 

efficiencies. A more detailed description of these inputs 

for the various mobile and stationary source categories is 

contained in the draft RIA.[3] It is sufficient here to 

note that for mobile sources, the model reflects the 

continuing gains in emissions control that accrue from the 

Federal Motor Vehicle Control Program, under which 

increasingly stringent exhaust and evaporative emission 

standards have been promulgated. For stationary sources, 

the model accounts for the emission reductions that have 

been achieved as of the base year (i.e. , 1983) from which 

the projections begin.* 

* This represents a conservative assumption for some of 

the urban areas modeled, because some states may 

further control existing stationary sources. The 

degree of such control, however, is currently unknown. 

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Figure 1 illustrates EPA's general projections of 

non-methane hydrocarbon (NMHC) emissions and ozone NAAQS 

attainment status for the years 1988, 1995, 2000, and 2010 

assuming no additional VOC control measures are promulgated 

in the future. The results for 1988 indicate that a 

substantial number of urban areas (51 of the 61 modeled) 

may fail to comply with the NAAQS by the statutory 

deadline. Beyond that, the most obvious trend between now 

and 1995 is that only a very small improvement in air 

quality is projected to occur as a result of the emission 

standards that already have been promulgated for both 

stationary and mobile sources. Since most of the major 

urban areas modeled (i.e., those with the greatest 

populations) remain in non-attainment status throughout the 

projection period, the small improvement shown thru 1995 

becomes even smaller when viewed in terms of population 

exposed to high ozone levels. 

Figure 1 also illustrates that in the more distant 

future, growth will cause the problem to worsen without 

further controls. More specifically, these projections 

indicate that by early in the next century, emission 

inventories will again be rising steadily. By the end of 

the projection period (i.e., 2010), emission inventories in 

the areas modeled apparently will be worse than in 1988. 

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RGURE1 

NMHC Inventories and Ozone NAAQS Attainment Status 

for 61 Urban Non-Attainment Areas - Base Case 

10000 

W 

c 

_g 

o 

o 

o 

c 

.2 

Cfl I 

o 

0) 

• M M 

B 

Q_ 

9000H 

8000 

7000-

6000-

5000-

4000-

3000-

i 2000-

1000-

55 

60 

o 

0) 

50 

c 

a> 

E 

c 

40 [O 

< 

I 

c 

30 5 

-20 

-10 

E 

a) 

-•"•--

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(D 

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-0 a. 

1988 1995 2000 2010 
P.26 

The number of areas violating the ozone NAAQS follows this 

trend.* 

The magnitude of the ozone air quality problem facing 

the nation is further illustrated by additional estimates 

made by EPA. The results of this analysis show the 

emission reductions that are needed relative to the 1983 

base-year NMHC inventory to eliminate the projected nonattainment problem. As shown in Table 1, reductions of up 

to about 90 percent appear necessary to bring all areas of 

the country into compliance. Based on estimates by the 

Table 1 

EFFECT OF VOC INVENTORY REDUCTIONS ON 

OZONE NAAQS COMPLIANCE SITUATION 

(61 NON-CALIFORNIA AREAS) 

% Reduction from Baseline No. of Non-Attainment Areas 

VOC Emissions Inventory** 

10% 

20% 

30% 

40% 

50% 

60% 

70% 

80% 

90% 

1988 

42 

32 

24 

16 

9 

3 

1 

1 

0 

1995 

38 

28 

24 

14 

9 

4 

2 

1 

0 

2000 

42 

31 

24 

17 

10 

5 

3 

1 

0 

* Given the uncertainties inherent in projecting 

absolute values for emission inventories and 

attainment status into the next century, it is more 

appropriate to emphasize the trends in these measures. 

** Beyond those that will already accrue from the 

existing Federal Motor Vehicle Control Program in the 

61 non-attainment areas modeled. 

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Agency's Ozone Task Force, there is a clear need to 

implement all reasonable controls on volatile organic 

compounds (VOC) if progress toward attainment of the ozone 

NAAQS is to be assured. Further, EPA has concluded that 

refueling controls, either Stage II or onboard, could 

provide part of the needed VOC reductions. 

Other Areas. While the benefits associated with 

controlling VOC emissions in non-attainment areas arereadily apparent, reducing these emissions in attainment 

areas is also beneficial. The benefits accruing from these 

reductions can be grouped into three categories. First, 

ozone is a regional concern because VOC emissions 

originating in one area may be transported through the 

atmosphere and adversely affect air quality in another 

area. This phenomenon allows VOC emissions in attainment 

areas to exacerbate problems in complying with the ozone 

NAAQS in non-attainment areas. Thus, the Agency believes 

that reducing such attainment area emissions is of value in 

terms of non-attainment area reductions. Second, Section 

110 of the CAA makes it clear that in addition to attaining 

the NAAQS, a primary purpose of the statute is to maintain 

compliance with the ambient standards in order to prevent 

the adverse health and welfare effects associated with 

excess concentrations of pollutants such as ozone. 

Similarily, Section 101(b)(1) provides that- a key purpose 

of the Act is to "protect and enhance the quality of the 

Nation's air resources so as to promote the public health 

-26-
P.28 

and welfare ...."* These goals apply to all areas of the 

country, including attainment areas. Thus, VOC control 

measures that help maintain the ozone NAAQS, or prevent the 

deterioration of air quality, in attainment areas have 

value for those purposes. Therefore, the benefits of VOC 

reductions in attainment areas, as well as non-attainment 

areas, are an important consideration in the overall 

evaluation of refueling controls. 

2. Refueling Emissions as a Carcinogenic Risk 

In addition to the health and welfare risks posed by 

ozone, of which refueling emissions are a precursor, EPA 

has found that gasoline vapor is probably carcinogenic to 

humans. Generally, quantifying the cancer risk posed by an 

environmental threat is an inexact science that, by 

necessity, relies on a variety of estimates and 

assumptions. Due to the complexity of the subject, it is 

important to understand the basis of EPA's carcinogenic 

risk assessment for refueling emissions before describing 

the results of the analysis. Therefore, an overview of the 

basis of EPA's risk analysis will precede the presentation 

of the actual cancer incidence estimates. For a more 

detailed discussion of the results of the risk assessment, 

the interested reader is referred to the draft RIA.[3] 

See Sierra Club v. EPA, 540 F.2d 1114 (D.C. Cir.), 

vacated (on other grounds) sub nom Montana Power 

Company v. EPA, 434 US 809 (1977). 

-27-
P.29 

The ambient concentrations of benzene and gasoline 

vapors generated from refueling operations are quite low, 

especially compared to animal exposures in laboratory 

studies. Moreover, it is impossible to directly measure 

the risk of contracting cancer using the analytical 

techniques which are currently available. As an 

alternative, EPA has estimated the cancer risk at these 

concentrations by extrapolating from estimates of risk due 

to higher concentrations in the studies of workplace and 

laboratory exposure. Thus, the estimated risks from these 

low concentrations represent plausible upper limits on the 

actual risk. 

Using this approach, the assessment of carcinogenic 

risk can be separated into two very broad categories. The 

first is estimating the potency of the active agent in 

causing a particular carcinogenic end point. The more 

potent the agent, the more probable it is that a person may 

contract cancer after being exposed to the substance over a 

period of time. The second broad category involves 

estimating the degree of exposure to the substance. This 

includes such variables as the number of individuals 

exposed, in addition to the concentration and duration of 

the exposure. Of the two broad categories, estimating the 

potency of a suspected carcinogen is often the most 

critical and difficult to quantify. Hence, in assessing 

-28-
P.30 

the carcinogenic risk associated with refueling emissions, 

it is especially important to acknowledge the principal 

uncertainties in this area. 

As already mentioned, the carcinogenic concerns 

associated with the refueling process have historically 

focused on benzene, a normal constituent of gasoline, and 

gasoline vapors as a whole. The cancer risk associated 

with benzene has been widely evaluated in both 

epidemiological and animal studies. The epidemiological 

studies have shown an increased incidence of leukemia among 

workers exposed to benzene. Both rats and mice have shown 

a statistically significant increase in carcinogenesis 

associated with relatively high benzene exposures through 

inhalation and ingestion. Additionally, the dose-response 

relationships derived from the human and animal studies 

were similar. The Agency believes this evidence provides 

an adequate basis for classifying benzene as a human 

carcinogen and for estimating the carcinogenic potency of 

this compound at the lower exposure levels that are typical 

of refueling operations, because the studies are of good 

quality and they show consistent results. 

As discussed earlier, the Agency listed benzene as a 

hazardous air pollutant under Section 112 of the CAA in 

1977 (42 FR 29332), based on the results of the 

occupational studies and EPA's finding that "ambient 

-29-
P.31 

exposures [to benzene] may constitute a cancer risk and 

should be reduced." in 1984, the potency estimate derived 

from these studies was used by EPA to establish standards 

for "fugitive" benzene ' emissions from stationary source 

equipment leaks (49 FR 23513). 

The quantitative estimate of risk from benzene 

exposure has been updated based on a recent review of the 

scientific literature.[7] The cancer potency estimate was 

increased slightly (i.e., 17 percent), and this updated 

estimate is used in the risk analysis accompanying this 

proposal. 

Like benzene, the carcinogenic risk associated with 

exposures to gasoline vapors as a whole has also been 

assessed by evaluating existing epidemiological and animal 

studies. The available epidemiological studies of workers 

in the petroleum industry are considered to be suggestive 

of increased cancer incidence. However, due to 

methodological difficulties in distinguishing between 

gasoline exposures and other chemicals, the Agency 

considers these studies to be inconclusive concerning the 

casual role of gasoline vapors at this time. As a result, 

the carcinogenic risk of exposure to gasoline vapors has 

been estimated largely on the basis of animal studies 

conducted by the American Petroleum Institute (API). In 

the API work, rats and mice were exposed to relatively high 

-30-
P.32 

concentrations of wholly vaporized unleaded gasoline for 

two years. These well designed, chronic inhalation studies 

showed evidence of significantly increased kidney cancer in 

male rats and liver cancer in female mice. The Agency's 

refueling risk assessment is based on the potency estimates 

from the male rat tests. However, the quantitative risk 

estimates derived by EPA from both animal species were in 

close agreement. 

The carcinogenic activity observed in . these animal 

tests is thought to be induced by active agents contained 

in the fuel other than benzene. This is a reasonable 

assumption, since the sites of carcinogenic activity are 

generally observed to be different for benzene than for 

gasoline vapors (i.e., circulatory system and bone marrow 

vs. liver and kidney), and since the concentration of 

benzene during the animal experiments was too small to 

induce the observed response. In estimating human risks to 

gasoline vapor, the risk of the benzene component itself is 

added to the human-equivalent gasoline vapor risk 

determined from the animal experiments, since the two 

effects are apparently independent of each other and 

additive at low concentrations. Such an approach for 

estimating the potential risks posed by a mixture of 

carcinogens is suggested in EPA's Carcinogen Risk 

Assessment Guidelines (51 FR 33992). 

-31-
P.33 

The use of animal data in carcinogenic risk 

assessments is a generally accepted practice when 

epidemiological evidence is inconclusive. In this 

particular case, the Agency finds the induction of tumors 

in two animal species provides adequate evidence to 

consider gasoline vapor as a probable human carcinogen 

under both EPA's Carcinogen Risk Assessment Guidelines and 

the criteria established by the International Agency for 

Research on Cancer. Also, the EPA believes the evidence is 

sufficient to justify a quantitative estimate of human risk 

from exposures to gasoline vapors in order to gauge the 

magnitude of the potential public health problem. 

Nevertheless, extrapolating test results from highly 

exposed animals to humans that are exposed to much lower 

concentrations in the ambient air is inherently uncertain, 

and the Agency's analysis recognizes these uncertainties. 

Due to the importance of the issues involved, the 

basis of EPA's risk assessment has been independently 

reviewed by the Agency's Science Advisory Board (SAB) and 

the Health Effects Institute (HEI). Both of these 

scientific groups generally agree that gasoline vapors are 

probable human carcinogens; however, they also have 

recognized the uncertainties inherent in extrapolating 

animal data to quantify human risk. 

-32-
P.34 

In reviewing EPA's risk assessment, SAB concluded that 

the degree of scientific uncertainty in the resulting 

quantitative estimate of human risk should be clearly 

acknowledged. HEI expressed a more cautious view regarding 

the actual quantification of carcinogenic risk, stating 

that it is not presently possible to draw accurate 

conclusions concerning the degree of human risk. 

In SAB's opinion, the two areas of greatest 

uncertainty in EPA's analysis of gasoline vapors are: 1) 

the relevance of using a quantitative risk factor based on 

the male rat kidney response in human quantitative risk 

estimates, and 2) the difference in chemical composition 

between the gasoline exposures in the API laboratory 

studies and that typical of actual population exposure 

during refueling emissions. Similar opinions have also 

been expressed by HEI and API. 

Regarding the first area of uncertainty, some 

investigators have argued that the male rats used in the 

chronic inhalation studies may be unique in their 

susceptibility to kidney cancer after being exposed to 

gasoline vapors. The male rat has been shown to be 

susceptible to renal toxicity (i.e., kidney cell damage) 

from gasoline vapors, and some scientists postulate that 

such damage ultimately leads to the, development of tumors. 

Further, the mechanism of this toxic response is thought to 

-33-
P.35 

be unique to the male rat species used in the laboratory 

studies. Such a finding of uniqueness in the male rat 

would weaken, but not eliminate, the presumption of a 

carcinogenic response in humans. 

The Agency finds several reasons to question the 

conjecture that the male rat responds uniquely to gasoline 

vapors. First, the link between acute or chronic 

hydrocarbon-induced kidney damage and carcinogenicity is 

not clear, nor has it been proven. Second, the kidney of 

experimental animals has been demonstrated to be the target 

organ of over 100 carcinogenic compounds. Third, a 

statistically significant increase in liver tumors was 

detected for female mice in the API studies, with no report 

of accompanying tissue damage. Finally, other types of 

malignant tumors have appeared in other strains of animals 

when exposed to synthetic fuels. 

Overall, most scientists agree with EPA that the role 

of acute kidney toxicity in the induction of kidney tumors 

in male rats and its relevance to human cancer are 

currently unresolved issues. However, it is important to 

note that a carcinogenic response to gasoline vapors was 

also demonstrated in the API laboratory studies of female 

mice. Further the Agency, HEI, and SAB all agree that the 

carcinogenic effect of gasoline vapors in animals is real 

and can not be ignored as a potential human hazard. 

-34-
P.36 

Regarding the second area of uncertainty raised by SAB 

and HEI, EPA agrees there may be a difference between the 

vapor composition to which animals were exposed in the 

chronic inhalation study and that to which humans may be 

exposed under ambient conditions. As previously discussed, 

refueling emissions consist of a greater proportion of 

"light-end" hydrocarbon molecules than does wholly 

vaporized gasoline. Due to the obvious differences in 

chemical composition, it is possible that the carcinogenic 

potential of gasoline vapors emitted during refueling is 

not well represented by the test results derived from 

wholly vaporized gasoline. API, among others, has 

specifically made this claim. 

In support of its position, API has performed 

short-term bioassay screening tests using different 

fractions of vaporized gasoline to identify the hydrocarbon 

compounds that initiate the renal toxicity observed in the 

male rat kidney. These tests showed branch-chain paraffins 

with 6 to 9 carbon atoms (i.e. , _> C6 compounds) to be the 

primary causal agents of the toxic effects. As a result, 

API has concluded that because the percentage of _>

 c« 

compounds in wholly vaporized gasoline is substantially 

more than in refueling vapors, EPA's estimate of the 

potential cancer risk from gasoline vapors is overly 

conservative. Specifically, the refueling vapor fraction 

composed of _> C6 hydrocarbons molecules has been shown to 

-35-
P.37 

be 25 percent or less of that in wholly vaporized 

gasoline. Thus, if API is correct, EPA's quantitative 

assessment of population risk to gasoline vapors would be 

too high by at least a factor of four. 

The Agency has considered API's argument, but notes 

that the crucial evidence demonstrating the association 

between kidney toxicity and kidney tumors is lacking. 

Also, SAB concluded "... that the issue of the 

representativeness of the inhaled vapors, while certainly a 

complicating factor in the API bioassay should not be 

regarded as a major flaw." In addition, EPA could find no 

data to indicate which fraction of the gasoline vapor is 

responsible for the induction of liver tumors in female 

mice. For these reasons, the Agency believes it would be 

unwise to base the quantitative risk assessment on an 

assumption that may significantly underestimate the 

potential health problem. Instead, EPA finds it prudent to 

interpret the results of the risk assessment as plausible 

upper limits, with the actual risks being at or below the 

estimates. Nonetheless, to illustrate the effects of the 

assumption that the heavier molecular weight compounds are 

responsible for the carcinogenic properties of refueling 

emissions, EPA has included an estimate of the incidences 

attributed to the >C6 fraction of gasoline vapors in its 

risk assessment. 

-36-
P.38 

Using the potency estimates for benzene and gasoline 

vapors described above, the risk assessment analysis 

focused on four exposure scenarios: occupational, 

self-service, community, and excess evaporative emissions. 

Each of these exposure scenarios can be characterized in 

terms of the intensity, frequency, and duration of 

exposure; the number of people affected; and the geographic 

range of emissions. 

The occupational exposure scenario, in terms of 

refueling emission control, is a rough estimate of the 

potential risk to service station attendants exposed to 

gasoline vapor. The purpose of this analysis was to give 

EPA an approximation of potential risks posed to 

individuals chronically exposed to gasoline vapor in the 

occupational setting. 

Self-service exposure refers to the exposure persons 

are subjected to in refueling their own vehicles. Like 

occupational exposure, it is characterized by high gasoline 

vapor concentrations for relatively brief durations. 

However, the frequency of exposure is much lower than that 

to which service station attendants are subjected. The 

rapid expansion of self-serve gasoline outlets means that, 

today and for the foreseeable future, the majority of the 

population experiences such exposure. 

-37-
P.39 

Community exposure refers to the exposure experienced 

by persons residing in the immediate vicinity of service 

stations. As such, it has a wider geographic range than do 

the occupational or self-service scenarios. The dispersion 

of gasoline vapor into the atmosphere in the vicinity of 

service stations means that the concentration of gasoline 

vapors is much lower than that of the preceding scenarios. 

However, the duration of such exposures is much longer, 

approaching constant exposure in the case of 24-hourstations. 

For each scenario, the estimated annual incidences are 

summarized in Table 2. The column headed "Bz" refers to 

incidences resulting from exposure to benzene. The column 

headed "GV" refers to incidences resulting from exposure to 

gasoline vapor as a whole. While the benzene exposure 

occurs as part of the exposure to gas vapor, EPA is 

treating these risk and incidence estimates as additive, 

for reasons already outlined. Thus, adding the "Bz" and 

"GV" estimates gives the estimated total incidences by 

scenario. In light of the uncertainties associated with 

these values, the Agency again believes they should be 

interpreted as plausible upper bounds of risk for possible 

effects. 

-38-
P.40 

Table 2 

ESTIMATED TOTAL CANCER INCIDENCES 

RESULTING FROM UNCONTROLLED REFUELING EMISSIONS 

Scenario 

Occupational 

Self-serve 

Community 

(Annual 

Bz 

2 

5 

1 

Incidence 

> cs 

4 

8 

3 

1987 -

GV 

17 

33 

10 

- 2020) 

Total* 

(Bz + GV) 

19 

38 

10 

Total * 7 15 60 67 

Columns and rows may not add exactly to totals due to 

rounding. 

The column in Table 2 headed "K V refers to the 

estimated incidences resulting from exposure to that 

fraction of gas vapor composed of "heavy-end" hydrocarbon 

compounds. These values are presented to illustrate the 

effects of using only these heavier compounds to evaluate 

the carcinogenic risk associated with exposures to gasoline 

vapors. 

In addition to the annual incidences, which are based 

on "average" exposures, EPA also estimated the lifetime 

risk for individuals highly exposed to gasoline vapors for 

each of the refueling-related exposure scenarios. The 

lifetime risks are 4 x 10"J, 8 x 10"s, and 1 x 10"4 

for occupational, self service, and community exposures, 

respectively. 

-39-
P.41 

The results of EPA's assessment show that the highest 

lifetime risk of cancer is incurred by service station 

attendants. The lowest lifetime risk is for individuals 

using self-service pumps. These individuals may 

potentially be exposed to significant vapor concentrations 

from the fillneck, but the number of refueling events is 

far lower than for the occupational category. Nonetheless, 

as shown in Table 2, self-service exposure shows the 

greatest annual cancer incidence because of the large 

number of people that pump their own gasoline. The upper 

bound of annual incidences (i.e. , Bz plus GV) for all 

refueling categories is estimated to be about 67. Of this, 

about 90 percent are attributable to gasoline vapors, with 

the remainder attributed to benzene. 

D. Overview of Alternative Control Techniques 

As mentioned earlier in this notice, there are two 

basic alternatives for the control of refueling emissions. 

These are generally referred to as "Stage II" and 

"onboard." The two vapor recovery systems are vastly 

different, with Stage II equipment installed at the service 

station and onboard equipment installed in the vehicle. 

This difference makes a basic understanding of the two 

control techniques especially important in facilitating the 

subsequent discussion of EPA's decision rationale. With 

this goal in mind, the following discussion presents a 

-40-
P.42 

brief description of the Stage II and onboard systems, and 

explores a few of the more important features associated 

with each technology. 

1. Basic Description of Stage II and Onboard 

Stage II vapor recovery systems, as noted earlier, are 

installed at the service station. With these systems, the 

vapor in the vehicle fuel tank that is displaced by liquid 

gasoline being dispensed is prevented from escaping to the 

atmosphere by a flexible rubber "boot" at the juncture of 

the fillneck and the dispensing nozzle. This boot is 

fitted over the nozzle's spout, and is attached to a hose 

similar to (but generally smaller than) the liquid 

dispensing hose. This hose, in turn, is connected to 

piping which routes the vapors to the underground fuel 

tank. A vapor-for-liquid exchange is made as liquid 

gasoline displaces gasoline vapor from the vehicle fuel 

tank to the underground storage tank. 

Recovering the vapor in this manner eliminates the 

ingestion of air by the underground tank that would 

normally occur as fuel is pumped out. This, in turn, 

prevents gasoline from evaporating inside the storage tank 

to reestablish the vapor-liquid equilibrium, as discussed 

earlier. The service station owner realizes an economic 

benefit from this recovered vapor, since liquid fuel that 

-41-
otherwise would be evaporated can instead be sold. This is 

referred to as the vapor recovery credit,* and will be 

cited by that term in the economic impact discussion later 

in this notice. 

Stage II systems can be subdivided into two broad 

types on the basis of the method used to return the 

displaced vapor to the underground storage tank. The first 

type, known as the "balance system," is the simpler, less 

expensive, and more widely used of the two (Figure 2). 

(About 80 percent of current Stage II system installations 

are balance systems.) Vapor transfer to the storage tank 

is accomplished by exploiting the slight pressure created 

in the vehicle fuel tank by the incoming flow of gasoline. 

This system is "passive," and operates on the basis of very 

small differences in pressure. Therefore, a tight seal is 

required at the juncture of the dispensing nozzle and the 

fillneck. In order to ensure a good seal, the dispensing 

nozzle in a balance system is equipped with a "no-seal, 

no-flow" feature, consisting of a spring-loaded bellows and 

an interlock mechanism. For fuel to be dispensed, enough 

Similarly, if Stage II is in place, the vapor from the 

underground tank that normally would be lost as this 

tank is refilled can be recycled back to the cargo 

truck via a vapor return line for subsequent 

reprocessing. 

-42-
Figure 2 

STAGE II VAPOR RECOVERY BALANCE SYSTEM 

METER 

GASOLINE FILL LINE 

GASOLINE STORAGE TANK 
P.45 

pressure must be applied to the nozzle by the operator to 

sufficiently compress the bellows and thus deactivate the 

interlock mechanism. 

The other broad type of Stage II system is known as 

"vacuum assist." Such systems enhance the recovery of 

gasoline vapor by employing a device (i.e., a blower or an 

aspirator) to create a slight vacuum at the nozzle. This 

vacuum acts to actively draw (assist) the gasoline vapor 

into the rubber boot for return to the storage tank. This 

vacuum assist is advantageous in that it obviates the need 

for a tight seal at the fillneck/nozzle juncture, but has 

the disadvantage that ambient air is drawn into the vapor 

return hose along with the vapor. For blower-assisted 

systems, this results in the total volume of the returning 

vapor-plus-ambient air being greater than the volume of 

liquid gasoline withdrawn from the underground tank. The 

excess vapor, which cannot be accommodated by the storage 

tank, thus requires some form of secondary processing 

(e.g., incineration). The complexity and added hardware 

associated with the vacuum assist system make it more 

expensive than the balance system, and it is significantly 

less popular for those areas currently employing Stage II 

vapor recovery. 

-44-
P.46 

The second basic alternative for the control of 

vehicle refueling emissions is the onboard vapor recovery 

system (Figure 3). As implied by the name, the requisite 

control hardware is located on the vehicle. Consequently, 

no discernible modifications to the fuel dispensing 

equipment are required, and consumers perceive no 

difference when dispensing fuel. Onboard systems function 

during the refueling of the vehicle by sealing the vehicle 

fillneck, then routing the displaced vapor from the fuel 

tank to a storage canister. This canister is loaded with 

granules of activated carbon, and the hydrocarbon molecules 

in the vapor are absorbed onto the surfaces of these 

granules. When the vehicle's engine is started, fresh 

(ambient) air is drawn through the canister to desorb, or 

purge, the hydrocarbons from the activated carbon. . The 

resulting mixture of air and hydrocarbon vapors is 

transferred to the fuel metering system and then burned in 

the engine. This provides the onboard system with a fuel 

recovery credit similar to that previously described in 

connection with Stage II, because gasoline vapors that 

would normally be lost to the atmosphere are instead used 

to power the vehicle. 

The Agency would like to add, however, that although 

the onboard vapor recovery system most widely discussed at 

the present time is based on the use of a charcoal storage 

canister, other alternative control technologies do exist. 

-45-
Figure 3 

Onboard Vapor Control System 

FUEL CAP 

NOZZLE ACTUATED 

ROLLOVER/VENT VALVE 

^J-TUBE SEAL 

\ 

DESIGNED SLOW LEAK 

VAPOR LINE 

/ 

LIMITING ORIFICE 

PURGE VALVE 

CARBON 

CANISTER 

TO PURGE 

INDUCTION 

POINT 

VEHICLE FUEL TANK 
P.48 

One such alternative, which is described in more detail in 

Section VI of this notice, is a flexible fuel tank 

bladder. The use of a bladder-based system is an 

attractive possibility not only because of its 

effectiveness in controlling refueling vapors, but also 

because this type of technology can improve vehicle safety 

beyond present levels in the event of a crash. EPA 

encourages the full exploration of this and any other 

alternative control technologies. Specifically, comments 

are requested on the advantages and disadvantages of 

alternatives to canister-based onboard controls, including 

the areas of technical feasibility, control effectiveness, 

and cost. 

2. Salient Features of Each Control Technique 

Onboard Refueling Controls and Evaporative Emissions. 

An issue closely associated with reducing emissions during 

the refueling process is the interaction between the 

requisite onboard control technology, fuel volatility, and 

the potential for reductions in evaporative emissions from 

motor vehicles. Recent data from EPA's in-use surveillance 

program* indicate that many vehicles fail to comply with 

* This test program is conducted by EPA to determine if 

vehicles that are certified to be in compliance with 

specific emission standards continue to meet the 

applicable requirements in day-to-day service. 

-47-
P.49 

the applicable evaporative emission standards in customer 

service.[8] A contributing cause of these failures is that 

in-use fuel typically is more volatile than fuel used in 

emissions certification testing and generates a greater 

volume of evaporative emissions. Evaporative emission 

control systems, if designed solely for use with 

certification fuel, may be undersized and insufficiently 

purged when used to control in-use fuel of a higher 

volatility than the fuel specified for certification, 

resulting in excess evaporative emissions. 

The Agency has identified several ways to help assure 

in-use compliance with the evaporative emission standards. 

The possible solutions generally reflect EPA's intent to 

have the volatility of certification fuel represent that of 

in-use fuel. In particular, in a separate proposed 

rulemaking, contained elsewhere in today's Federal 

Register, EPA proposes to reduce the Reid Vapor Pressure 

(RVP) (a volatility measure) of commercially available 

gasoline in Class C areas (as defined by the American 

Society of Testing Materials) in two stages, from the 

current recommended summertime maximum of 11.5 pounds per 

square inch (psi) to 9.0 psi (the volatility level for 

certification test fuel) by 1992.* Volatility levels in 

* The Agency's volatility rulemaking considers RVP 

changes as low as 8.0 psi. 

-48-
P.50 

other areas of the country would be reduced proportionally. 

This would help assure that evaporative control systems are 

designed and tested to handle fuel volatility 

representative of what they will encounter in-use. 

Another approach to attaining the evaporative 

standards would be to increase the volatility of the 

certification test fuel to match that of commercial fuel. 

If done in conjunction with relatively simple revisions to* 

the current test procedure, this revision would basically 

require the use of larger storage canisters and/or higher 

purge rates to control excess evaporative emissions. 

This last approach is also evaluated in EPA's 

volatility proposal and is assumed in the base analyses in 

support of today's refueling proposal. In particular, the 

refueling analyses presume a certification test fuel RVP of 

11.5 psi, rather than the current certification requirement 

of 9.0 psi. The Agency chose this approach for analyzing 

the impact of volatility controls on refueling controls 

because a certification RVP of 11.5 psi not only represents 

the highest in-use volatility level currently used in the 

vast majority of non-attainment areas as specified by the 

American Society for Testing and Materials during the 

summer ozone season, but also is a worst-case situation 

with respect to the cost and design, of onboard controls. 

-49-
P.51 

In its final rulemaking, the Agency will ensure that the 

volatility of the certification fuel for onboard refueling 

controls is fully consistent with the final decisions made 

about test fuel in the volatility rulemaking. 

If EPA reduces the volatility of commercial fuel, the 

costs and benefits of refueling controls would change, 

although the effect is relatively small. EPA has analyzed 

these effects for the range of volatility limits proposed 

in the volatility rulemaking. These effects and their 

interactions with the Agency's decision to control 

refueling emissions are fully discussed in Section V of 

this proposal. The analyses accompanying the final onboard 

rule will reflect the actual in-use volatility of 

commercial fuel as specified by the final volatility rule. 

In the context of solving the evaporative emissions 

problem, it is also important to understand that onboard 

refueling controls would generally be designed with the 

inherent ability to control excess evaporative emissions. 

This is possible because these systems are similar in 

design and function to evaporative control systems. If 

onboard were combined with the control of excess 

evaporative emissions in this manner, the resulting cost 

effectiveness of the reductions of excess HC emissions 

would be more attractive than the control of only refueling 

emissions. The Agency's draft gasoline marketing study 

-50-
P.52 

used this approach. However, because EPA is proposing to 

address the excess evaporative emissions problem by 

controlling fuel volatility, the Agency believes it is most 

appropriate to determine the best refueling control 

strategy exclusive of excess evaporative emissions 

control. Therefore, the costs and benefits of eliminating 

excess evaporative emissions are excluded from EPA's 

analysis of refueling controls and the associated decision 

rationale (i.e., onboard is analyzed incrementally to the 

control of excess evaporative emissions). Instead, they 

are considered in the separate EPA rulemaking action on 

fuel volatility and excess evaporative emissions contained 

elsewhere in today's Federal Register. 

User Convenience. Regardless of their design, all 

Stage II systems share a common drawback in that the 

recovery nozzles and hoses are somewhat heavier, bulkier, 

and more awkward than their conventional counterparts. 

Even though the overall inconvenience associated with Stage 

II systems of more recent design has been greatly reduced 

from early systems, the Agency believes that some small 

inconvenience factor is, and will continue to be, 

associated with the consumer use of Stage II equipment. 

-51-
P.53 

The inconvenience of using Stage II equipment can be 

especially significant for balance systems, which are the 

dominant type of installation. The spring-loaded bellows 

and interlock mechanism associated with the "no seal, no 

flow" feature of these systems has some potentially 

inconvenient characteristics. The operator must exert 

pressure on the nozzle when inserting it into the fillpipe 

in order to compress the bellows, disengage the interlock 

system, and allow fuel to be dispensed. 

The interlock itself adds a possible failure mode to 

the refueling operation. In addition, for proper 

operation, the person conducting the refueling must wait 

several seconds after stopping the flow of fuel before 

removing the nozzle, in order to allow the pressure within 

the system to equalize. If the nozzle is removed too soon 

(as often happens) vapor loss may occur. Of course, the 

extent to which these characteristics of Stage II systems 

are perceived to be an inconvenience will vary by 

individual. 

Onboard vapor recovery systems, by contrast, remain 

unnoticed by the consumer during the refueling process. 

The requisite hardware is an integral, self-contained part 

of the vehicle, and there is no direct human involvement in 

the control process, since no special action or attention 

is required in order to dispense the fuel. Finally, 

-52-
P.54 

contrary to some vehicle manufacturers' claims, onboard 

systems are expected to be integrated within the vehicle in 

a way that will not interfere with occupant or trunk 

space. Hence, onboard systems avoid the consumer 

inconvenience often associated with Stage II systems. 

It should also be noted that both Stage II and onboard 

vapor recovery systems may present some benefit to the 

consumer in terms of: 1) personal discomfort due to 

breathing gasoline vapors, and 2) fuel spitback and 

spillage during the dispensing process. Stage II, of 

course, removes gasoline vapors from the breathing zone,* 

and the more recent generation of equipment appears to 

reduce the frequency of spitback. Similarly, onboard 

mitigates the inhalation of gasoline vapors. It also 

should reduce spitback, since the systems will be required 

to control this phenomenon at high dispensing rates as part 

of the certification process, which is discussed later in 

today's notice. In fact, because of this specific 

General Motors has examined the costs and benefits of 

using Stage II controls in California. Although the 

Agency does not endorse the conclusions of the study, 

the results suggest that consumers perceive a 

significant benefit associated with breathing fewer 

vapors when using Stage II equipment. If this is the 

case, EPA believes that onboard would also be 

perceived as providing this type of benefit, because 

it also reduces vapor inhalation. 

-53-
P.55 

regulatory requirement, it is possible that onboard may 

provide a somewhat greater benefit to the consumer in 

avoiding this particular annoyance than Stage II. 

The difference between onboard and Stage II in terms 

of user convenience is a significant distinction. The fact 

that consumers perceive no difference in refueling a 

vehicle equipped with onboard controls relative to a 

vehicle without such controls (or perhaps even someadvantages), means that one of the primary incentives for 

tampering with emission control systems does not exist for 

onboard. This is not the case with Stage II systems where 

tampering (e.g., substitution of conventional nozzles and 

hoses by station owners) may occur in an attempt to 

mitigate potentially annoying characteristics associated 

with the dispensing equipment. As discussed below, this 

difference has an impact on the projected relative in-use 

control efficiencies for the two systems. 

The inconvenience associated with the use of Stage II 

systems, as compared to onboard control, also can be 

assigned a certain economic value. If consumers would 

willingly pay more for their gasoline simply to avoid the 

use of Stage II dispensing equipment, then there exists a 

relative cost between the two control approaches which is 

defined as the Stage II "inconvenience cost." Due to the 

wide variation in which consumers may value Stage II 

-54-
P.56 

inconvenience, it is impossible to specifically quantify 

this cost. However, to provide an indication of the 

importance of this factor, the effect of small 

inconvenience costs will be indicated in the analyses 

presented below. 

Control Efficiency. Both Stage II and onboard vapor 

recovery systems have the potential to control nearly all 

refueling emissions. Certification tests of new Stage II 

installations by the State of California indicate that the 

systems initially are about 95 percent efficient. Test 

data for experimental onboard systems have shown control 

efficiencies as high as 99 percent. 

Of course, it is the in-use effectiveness that is 

important in assessing the environmental benefits 

associated with each control technology. This is 

determined by combining the theoretical efficiency of each 

system with estimates of the losses in control frequency 

and effectiveness resulting from such factors as 

misinstallation, improper maintenance, and tampering. The 

Agency's analysis of data from existing Stage II programs 

indicates that the frequency of the above events, and 

therefore the resulting in-use efficiency of the control 

technology, is highly dependent on the level of enforcement 

(e.g., inspections by state or local authorities). Based 

on these data, national average Stage II in-use efficiencies 

-55-
P.57 

were estimated by EPA to range from 62 percent, in areas of 

minimal enforcement (i.e., essentially no inspections), to 

86 percent, in areas with annual enforcement programs. EPA 

would expect enforcement to vary between these extremes 

throughout the country. 

Unlike Stage II systems, which have been in use in 

certain areas of the country for several years, onboard 

systems have yet to be used in production vehicles. 

Consequently, there are no extensive in-use data on the 

performance of production versions of this technology. 

However, EPA notes that prototype onboard systems have been 

installed in in-use vehicles and have successfully 

accumulated more than 50,000 miles of service at the 

theoretical maximum level of control, providing evidence of 

successful in-use performance. 

In such cases, where specific in-use data is lacking, 

in-use data from similar control technology is often used 

as a surrogate for the purpose of analysis. This approach 

is particularly useful here, in that EPA has a significant 

amount of surveillance survey data for evaporative emission 

control systems, which are very similar in design and 

function to onboard vapor recovery systems. Because of 

these similarities, EPA anticipates that the in-use 

performance of onboard systems in capturing vapors 

displaced from the vehicle's fuel tank should be very much 

-56-
P.58 

like that of evaporative emission control systems that have 

been properly designed. In particular, little or no 

deterioration in performance over the useful life of the 

vehicle would be expected for properly maintained systems. 

Hence, using the rates of malmaintenance, defect, and 

tampering found for in-use evaporative storage canisters, 

EPA has estimated the in-use efficiency of onboard systems 

to be about 93 percent. This in-use efficiency is not 

directly comparable to the Stage II values discussed above, 

however, because onboard does not control the emptying 

losses from the service station's underground tank as Stage 

II controls do. If these losses are included in expressing 

the overall system efficiency for onboard, EPA estimates 

these controls capture about 83 percent of all refueling 

emissions. 

Exemptions. The installation of Stage II control 

systems requires a sizeable capital investment by service 

station owners. For many stations. Stage II control could 

be prohibitively expensive, resulting in significant 

economic hardship or even station closure. Section 324 of 

the CAA addresses this issue for smaller service stations 

by mandating that any independent facility with a 

throughput less than 50,000 gallons per month (gal/mo) be 

exempt from any Federal Stage II requirements promulgated 

by EPA. Additionally, the Agency's analysis of this issue 

showed that coupling the Congressionally-mandated 50,000 

-57-
P.59 

gal/mo exemption limit for independents with a 10,000 

gal/mo exemption limit for non-independents, which as a 

byproduct of their affiliation with petroleum companies may 

have greater economic resources, appeared to provide the 

most cost-effective Federal Stage II program. This 

exemption scenario was used extensively in the draft RIA, 

and results in about 75 percent of all public and private 

outlets (representing about 25 percent of the total 

gasoline consumption) being uncontrolled.[3] 

Although the CAA mandates that any Federally required 

Stage II program incorporate a 50,000 gal/mo exemption 

limit for independent stations (and although EPA could 

adopt a 10,000 gal/mo limit for non-independents to 

maximize cost effectiveness), if Stage II were selectively 

implemented in non-attainment areas, State governments 

could impose more stringent exemption levels than specified 

by EPA or simply not allow exemptions. As an example of 

other possible exemption levels, many areas of California 

with Stage II programs exempt stations with throughputs of 

less than 2,000 gal/mo.* Lower exemption levels have the 

advantage of providing greater emission reductions. One of 

the primary disadvantages is that the marginal cost of 

* Exemption levels in California non-attainment areas 

range from 0 - 30,000 gal/mo. 

-58-
P.60 

control increases significantly as smaller and smaller 

stations are added to the program. Also, the number of 

facilities escalates rapidly as the exemption limit is 

reduced, with a concomitant increase in the scope and 

difficulty of implementing, and then administering such 

programs. 

The Agency's sensitivity analysis of this issue showed 

that the incremental cost effectiveness of control rapidly 

escalates for stations with throughputs less than 10,000 

gal/mo. For example, VOC reductions from stations pumping 

between 2,000 and 10,000 gal/mo would cost more than nine 

times more on an incremental basis than the reductions 

provided under the 10,000/50,000 gal/mo Federal exemption 

scenario. Given the potential adverse economic effects of 

lower exemption levels, the Agency can not rule out the 

possibility that many States would decline adopting 

substantially lower exemption levels than might be required 

by EPA. Therefore, the Agency has assumed the 

10,000/50,000 gal/mo Federal exemption scenario in 

analyzing the costs and emission benefits of Stage II, 

while at the same time acknowledging that, if selectively 

implemented in non-attainment areas, individual States may 

prefer more stringent Stage II programs. 

•59-
P.61 

The existence of any Stage II exemptions effectively 

decreases the overall efficiency of the program with regard 

to reducing all the potentially controllable refueling 

emissions. If the exemptions provided under the 

10,000/50,000 gal/mo Federal limits are included in 

expressing the overall system efficiency for Stage II, EPA 

estimates these controls capture about 50-70 percent of all 

refueling emissions. The basis for this estimate is 

discussed more fully in Section II.E. of today's notice. 

By contrast, no analogous exemptions are necessary, or 

contemplated, for the classes of vehicles subject to 

onboard requirements.* 

Unit Cost. The estimated total capital cost of a 

Stage II vapor recovery system for the moderately-sized 

nonexempt service station is $12,200. When this is 

amortized over the expected lifetime of the equipment, and 

the annual operating expenses and fuel recovery credit are 

included, such a nonexempt service station will spend 

approximately $2,600 per year for vapor recovery controls. 

In the case of onboard control, when expressed as an 

Motorcycles and some off-road vehicles are the only 

vehicles potentially controlled by Stage II systems 

that would be exempt from onboard requirements. 

Off-road vehicles are not subject to control under 

Section 202 of the Act, while EPA would exempt 

motorcycles due primarily to either economic or 

technical feasibility considerations. 

-60-
P.62 

increment to the cost of reducing excess evaporative 

emissions, the vapor recovery system is estimated to 

increase the purchase price of the average vehicle by $19. 

If the anticipated fuel recovery credit for a 

well-maintained vehicle is discounted to the year of 

purchase and added to the above hardware cost, the average 

buyer will incur a net cost of about $14 per vehicle. 

Decision Rationale and Selection of Control 

Technology 

This section explains the Agency's overall rationale 

for proposing refueling controls in general, and for 

proposing onboard control technology in particular. In 

discussing whether refueling controls should be adopted, 

the costs and benefits of other strategies that have either 

been adopted or are under serious consideration will be 

used as comparative benchmarks. In choosing between the 

alternative control technologies, several important factors 

affecting the decision will be evaluated: emission 

reductions, cancer incidence reductions, timing of the 

benefits, cost, cost effectiveness, enforcement burden, 

user convenience, equity, and competitive effects. Some of 

these topics were introduced in the previous sections of 

today's notice, the others will be described where 

appropriate in the analysis which follows. 

-61-
P.63 

The overall presentation of EPA's decision rationale 

begins by focusing on refueling control as a strategy to 

reduce ozone precursor emissions in non-attainment areas. 

The presentation then focuses on the value of reducing VOC 

emissions in attainment areas and the reduction in 

carcinogenic risk that results from a refueling control 

program. 

1. Refueling Controls for Ozone NAAQS Attainment 

To assess refueling controls as an ozone reduction 

strategy in non-attainment areas, the Agency's analysis 

includes only the costs and benefits of implementing Stage 

II control technology in 61 urban non-attainment areas* 

outside of California, because Stage II is already in place 

there, as discussed previously. For onboard, the costs of 

a nationwide program are used (since onboard cannot be 

implemented solely in non-attainment areas), while the 

benefits are restricted to only those that would occur in 

the same 61 areas. 

Evaluating the two control technologies in this manner 

does not reflect the possible reduction in cancer 

incidences or the reduction in ozone levels in attainment 

*, This is the estimated number of non-attainment areas 

at the time this analysis was performed. 

-62-
P.64_ 

areas associated with onboard control requirements. It is 

clear, for example, that in addition to reducing the ozone 

health effects associated with non-attainment areas, 

essentially all reductions in ozone precursor emissions 

have potential value, even those occurring outside of 

non-attainment areas. Including these potential effects in 

the analysis would improve the estimate of onboard cost 

effectiveness. The additional benefits of a nationwide 

onboard program, and the effects of such benefits on costeffectiveness, are further discussed in Section II.E.3. of 

today's notice. 

Table 3 summarizes the results of EPA's non-attainment 

area analysis. It can be seen from this table that 

implementing either Stage II or onboard can provide a 

significant degree of VOC control in non-attainment areas. 

The range of potential emission reductions using Stage II 

is just less than or equal to about two percent of the 

total base year VOC inventory, while for onboard it is 

about two percent of the base year inventory. Few of the 

remaining VOC control strategies known to EPA can provide 

significantly more emission reduction in non-attainment 

areas, since the larger sources are already subject to 

emission control requirements. 

-63-
P.65 

Table 3 

VOC RESULTS FOR REFUELING CONTROLS 

IN 61 URBAN NON-ATTAINMENT AREAS 

Annual VOC Annualized Cost 

Reduction Costs Effectiveness 

Strategy (1000 Mg/Yr) ($MM/Yr) ($/Mg) 

Stage II* 66-100 58-92 850-1100 

(195-295**) (2700-3600**) 

Onboard no*** 180 2200**** 

* Stage II values are based on the 10,000/50,000 gal/mo 

Federal exemption scenario. 

** To illustrate the importance of even a small 

inconvenience cost, these numbers include an average 

inconvenience cost of about 10 cents per refueling 

event. This represents a cost of $137 to 203 MM/yr. 

An inconvenience cost of only about one half a cent 

per gallon (5 cents per fill-up) would make Stage II 

and onboard cost-effectiveness values similar.[3] 

*** Includes only reductions in 61 urban NA areas; 

nationwide reductions are 280,000 Mg/yr. 

**** As discussed later in this section, when the other 

benefits of an onboard program are included, the cost 

effectiveness becomes substantially better. 

To put the cost effectiveness of refueling control in 

perspective, the cost-effectiveness values in Table 3 can 

be compared to those of other control options that are 

available for non-attainment areas. In this regard, 

refueling emissions control remains within the 

cost-effectiveness range represented by other VOC reduction 

strategies, and appears significantly less expensive than 

some of the options which have been identified. (For 

example, controlling VOC emissions from metal rolling 

-64-
P.66 

operations has a cost effectiveness ranging up to 

$9,500/Mg.) Furthermore, as mentioned earlier, the other 

control programs are generally more difficult to implement 

relative to a refueling control program. 

From this information, it not only appears that the 

control of refueling emissions, whether by Stage II or by 

onboard, represents a significant reduction in VOC 

emissions,* but can be achieved with a cost effectiveness, 

in the range of other available control alternatives. 

If refueling emissions are to be controlled to obtain 

non-attainment area VOC emissions reductions, EPA must 

choose between the two alternative control technologies. 

Leaving aside the effect of inconvenience costs, the 

cost-effectiveness values in Table 3 favor Stage II. 

However, there are a number of other relevant factors which 

must be considered that make onboard controls more 

desirable overall than Stage II. 

First, viewing the expected emission benefits, Table 3 

shows onboard has the potential to provide greater emission 

Reductions in potential cancer risk are proportional 

to VOC reductions. This topic is further discussed in 

Section II.E.3. 

-65-
P.67 

reductions than Stage II in the long run.* This advantage 

of onboard stems from both the likelihood of somewhat 

higher in-use control efficiency and the lack of 

significant exemptions, relative to Stage II.** As shown 

in Figure 4, onboard reduces refueling emissions by 83 

percent from uncontrolled levels after full implementation. 

Onboard's long-term control capability far exceeds the 

range of 48 to 66 percent reduction (depending on level of 

enforcement) achieved by Stage II systems with the Federal 

exemption levels. This advantage is especially significant 

when it is recalled that the non-attainment problem is 

projected to become more severe after the mid-1990's and 

that few other currently available strategies identified by 

the Agency appear capable of providing a significant degree 

of VOC control. 

In the short-term, the comparison is less clear cut. 

Figure 4 shows that Stage II systems could provide greater 

emission reductions than onboard in the initial years after 

implementation, depending on what assumptions are made with 

respect to the implementation schedule of such systems. 

For more stringent exemption scenarios than the 

10,000/50,000 gal/mo Federal exemption level assumed 

in the analysis, the average annual emission 

reductions for onboard are at the mid-point in the 

range of possible values for Stage II.[3] 

Onboard appears to retain this long-term advantage, 

except when Stage II exemptions are allowed only for 

stations with throughputs of less than 2,000 gal/mo 

and annual enforcement is assumed. This exemption 

level is not consistent with Section 324 of the CAA. 

-66-
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P.69 

The maximum . advantage occurs under the assumption that 

Stage II systems could be fully installed in all 

non-attainment areas within a three-year period. By 

contrast, onboard controls would be phased-in over a longer 

period of time as new vehicles displace existing vehicles 

in the fleet. 

There is a degree of uncertainty associated with the 

3-year phase-in schedule for Stage II. The logistics and* 

resource requirements of equipping the large number of 

service stations in non-attainment areas with Stage II 

systems, and the potential for local resistance to such an 

extensive program make it very difficult to judge when full 

implementation would actually occur. The uncertain nature 

of any short-term advantage that may be associated with 

Stage II systems in terms of emission reductions is readily 

illustrated if a somewhat longer implementation schedule is 

assumed. For example, Figure 4 indicates that a seven-year 

implementation schedule, which has been suggested by API, 

as a reasonable schedule and which could occur in 

conjunction with the minimal enforcement scenario, would 

eliminate any short-term benefit of Stage II. 

The Agency believes there are two other considerations 

pertaining to VOC reductions that are important in choosing 

between onboard and Stage II in non-attainment areas. The 

first involves the fact that the nationwide scope of an 

-68-
P.70 

onboard program would provide automatic coverage for 

marginal attainment areas which may otherwise violate the 

standard in the future due to population or industrial 

growth. The second consideration involves the broad 

geographic nature of ozone air quality problems. This 

pollutant generally is a regional concern because VOC 

emissions in attainment areas may be transported through 

the atmosphere into adjacent non-attainment areas. 

Turning from the immediate issue of emission 

reductions, there are a number of practical areas where 

Stage II and onboard are quite different. Adopting Stage 

II in non-attainment areas across the country would result 

in an extensive new air pollution control program. For 

example, under the Federal exemption criteria assumed by 

EPA, the 61 non-attainment areas have about 43,000 service 

stations that would be affected. If individual states 

adopted more stringent requirements, this number would 

escalate rapidly. In most cases, Stage II programs would 

be implemented through action by each affected state 

government. In some cases, state legislative approval may 

be required. Individual states would then be primarily 

responsible for administration, inspection, and enforcement 

after implementation. While the existence of such 

complications is not, in itself, sufficient reason not to 

implement Stage II controls, it is another factor to be 

considered in the decision. 

-69-
P.71 

In a related area, an effective enforcement of Stage 

II programs would require annual inspections in order to 

ensure maximum in-use effectiveness. Hence, the increase 

in enforcement staff for states and local areas associated 

with a Stage II program would be quite significant. When 

the scope of these programs, the implementation and 

continuing enforcement costs, and the inconvenience 

associated with the dispensing equipment are all taken into 

consideration, EPA believes that Stage II vapor recovery 

could prove to be an unpopular control strategy at both the 

state and local government levels in many areas of the 

country, as numerous comments on EPA's gasoline marketing 

study tend to confirm. 

The number of different parties involved in the 

successful use of Stage II controls as an ozone reduction 

strategy could also have significant adverse impacts on the 

rate of implementation and in-use effectiveness of Stage 

II. It likely would lead to delays in the implementation 

of Stage II control systems in some areas, and even after 

implementation, there could be pressures operating against 

the concurrent establishment of strong provisions for 

inspections and enforcement. 

Onboard has none of these practical disadvantages. 

Onboard avoids the establishment of a multitude of new 

state and local programs with potentially large enforcement 

-70-
P.72 

burdens. Rather, this control technology would represent 

the addition of a new mobile source emission standard to 

the existing Federal Motor Vehicle Control Program that has 

demonstrated its success. In addition, it would be 

implemented, managed, and enforced in conjunction with the 

existing administrative and enforcement functions that 

already exist as part of the current motor vehicle 

program. Therefore, onboard holds a clear advantage over 

Stage II in terms of the implementation and enforcement 

aspects of a program to control vehicle refueling emissions. 

There are certain economic considerations that are 

also important in choosing between onboard and Stage II. 

These concern the distribution of costs and resultant 

effects on competition. The installation and maintenance 

of Stage II control systems clearly imposes a significant 

cost burden on service station owners, particularly those 

near the exemption level selected. 

Further, increased operating costs associated with 

maintaining Stage II systems could adversely affect 

competition between some controlled and uncontrolled 

stations. This could occur for stations located just 

within the boundary of a non-attainment area relative to 

their uncontrolled counterparts, or for controlled stations 

just above the exemption cutoff level relative to their * 

uncontrolled competition below the exemption level. 

-71-
P.73 

Such economic disruptions are avoided through the use 

of onboard systems, since the costs of control are spread 

across a much greater number of economic entities (i.e., 

all the purchasers of new automobiles and trucks). EPA 

believes that this distribution of costs is inherently more 

equitable than that for Stage II. Indeed, it is likely 

that because of this basic characteristic of onboard 

controls, Section 202(a)(6) of the CAA directed EPA to 

specifically consider the "equitable distribution of costs" 

in evaluating onboard control systems. 

It might be also argued, however, that an onboard 

program is not equitable because vehicle owners residing 

outside of non-attainment areas would be required to share 

the cost of a program directed primarily at non-attainment 

area benefits. As will be discussed below, the equities in 

this case are not so clear-cut, because there are 

potentially significant benefits from onboard controls in 

attainment areas. 

Finally, turning once again to the question of 

inconvenience costs, EPA believes that while it may be very 

difficult to assign a specific value to either the operator 

inconvenience attributable to Stage II or the various 

implementation and competitive disadvantages of Stage II 

just described, they clearly have some value. Referring 

-72-
back to Table. 3, it can be seen that even a small value for 

such inconvenience radically worsens Stage II cost 

effectiveness compared to onboard. In fact, an 

inconvenience cost of about one half a cent per gallon 

(multiplied by a large number of gallons per year) makes 

the Stage II and onboard cost-effectiveness values 

equal.[3] Hence, even ignoring the nationwide benefits 

inherent in an onboard program, EPA believes that onboard 

has many advantages over Stage II as a VOC control strategyfor non-attainment areas. 

2. Overall Benefits of Onboard Control 

This section provides EPA's overall assessment of the 

benefits of alternative refueling emissions control 

programs. Onboard, as a national refueling emissions 

control strategy, would provide additional ambient air 

quality benefits and direct health benefits throughout the 

country. The benefits of reducing emissions of ozone 

precursors in non-attainment areas are relatively obvious, 

and have been examined in detail in the preceding section. 

While the potential benefits of similar emission reductions 

in areas currently meeting the ozone NAAQS may not be as 

readily apparent, they are still important. In addition, 

benefits in terms of direct health effects (cancer risk 

reductions) occur in both attainment and non-attainment 

areas as a result of controlling refueling emissions. 

-73-
P.75 

The potential value of controlling ozone precursor 

emissions in attainment areas have been discussed earlier 

in this preamble. Such potential effects include the 

atmospheric transport of VOC emissions from attainment to 

non-attainment areas, making it more difficult to comply 

with the ozone NAAQS in regions with existing air quality 

problems. There are also a considerable number of areas 

which, while in attainment of the ozone NAAQS, are very 

close to the standard. VOC reductions in these areas can 

be expected to have a value similar to non-attainment area 

reductions if they are necessary to maintain compliance. 

These facts suggest that there is a benefit from a 

refueling emissions control program that achieves emission 

reductions in attainment areas as well as non-attainment 

areas. 

Reducing human exposures to refueling vapors also 

directly reduces the potential cancer risk associated with 

these emissions. EPA's estimates of these reductions are 

given in Table 4. Again, the numbers given here for Stage 

II reflect the fact that Stage II would be implemented in 

non-attainment areas only, since it has already been shown 

that on a nationwide basis onboard is more desirable than 

Stage II. Stage II incidence reduction benefits could, of 

course, be increased by implementing a nationwide program. 

However, under the Federal exemption limits, overall Stage 

-74-
P.76 

II benefits would not be as great as those for onboard, 

because of its lower overall efficiency and the fact that 

incidence reductions are proportional to emission 

reductions. 

Table 4 

INCIDENCE REDUCTIONS FROM STAGE II AND ONBOARD 

(Annual Incidence 1988 - 2020) 

Scenario Bz yCs GV 

Stage II l 2-4 10-15 

Onboard 4 io 38 

On the basis of overall control effectiveness, onboard 

produces larger cancer incidence reductions, because 

control is not confined to non-attainment areas only. 

Therefore, the numbers in Table 4 strongly favor an onboard 

program. These additional effects are certainly of value 

to society, just as are ozone reductions in non-attainment 

areas. They accrue without any added expense and can be 

viewed as partially offsetting the costs of ozone reduction 

in non-attainment areas. Therefore, giving some reasonable 

value to these effects will more accurately reflect the 

overall cost.effectiveness of refueling control. 

Assigning exact monetary values to ozone reductions in 

attainment areas and to the number of cancer incidences 

avoided is problematic, given the number of variables 

involved and the ways various segments of the society may 

-75-
P.77 

value the two types of benefits. Estimates for these 

values can be identified, however. For example, for VOC 

reductions in attainment areas, a value of $250/Mg has been 

cited by General Motors in a previous evaluation of 

hydrocarbon control benefits.[9] Although the Agency has 

not yet completed its own analysis of the best value to use 

for attainment area benefits, $250/Mg has been used in the 

analysis. Similarly, a range of $0.5 to $7.5 million per 

incidence avoided has sometimes been used by EPA and others 

to evaluate the benefits of reduced cancer risks. While 

the Agency does not endorse these specific values, they are 

useful when combined in various ways to evaluate the cost 

effectiveness of adopting refueling control as an ozone 

reduction strategy in the 61 urban non-attainment areas. 

If the values cited above for emission reductions in 

attainment areas and cancer incidences averted are combined 

with the cost-effectiveness analysis previously summarized 

in Table 3, the results shown in Table 5 are obtained. The 

first value ($2200/Mg for onboard) is taken directly from 

Table 3, and represents the case where costs are applied 

only to the VOC reductions occurring in the 61 

non-attainment areas. Subsequent entries in Table 5 

present the resulting cost-effectiveness for onboard VOC 

control in non-attainment areas if credits for other 

benefits are included as indicated. 

-76-
P.78 

Table 5 

VOC COST EFFECTIVENESS 

IN 61 URBAN NON-ATTAINMENT AREAS* 

Onboard Stage 

Quantity Being Valued ($/MG) ($/MG) 

VOC reductions in non-attainment (NA) 

areas only 2200 850-1100 

VOC reductions in NA areas, with benzene 

incidence reductions valued at $7.5 MM 1900 740-970 

VOC reductions in NA areas, with $250/Mg 

benefit for VOC reductions in 

attainment areas (AA) and benzene 

incidence reductions valued at $7.5 MM 1500 740-970 

VOC reductions in NA areas, with $250/Mg 

benefit for VOC reductions in AA and 

benzene and _>C6 incidence reductions 

valued at $7.5MM 850 460-640 

VOC reductions in NA areas, with $250/Mg 

benefit for VOC reductions in AA and 

benzene and all GV incidence reductions 

valued at $7.5MM Neg. Neg. 

In viewing the progression of cost-effectiveness 

values as various benefits are included in Table 5, note 

that the cost effectiveness of onboard rapidly improves. 

In fact, if all the potential benefits are included in the 

analysis, the VOC cost effectiveness in non-attainment 

areas becomes negative. This simply means that the value 

of all the benefits is greater than the cost of the onboard 

program. 

-77-
P.79 

However,, as discussed earlier, it is particularly 

difficult to accurately estimate the magnitude of the toxic 

impact of gasoline vapors given the scientific 

uncertainties involved. This uncertainty suggests that the 

non-attainment area VOC cost effectiveness for onboard is 

in the range from negative to $1500/Mg. EPA believes such 

cost-effectiveness values are well within the range of and 

generally lower than other available VOC control measures. 

Indeed, the overall desirability of onboard relative to* 

Stage II could make it preferable even if its cost 

effectiveness were substantially worse than that for Stage 

II. 

3. Conclusions 

The above analysis has presented the reasonableness 

and need for refueling control and the comparison between 

onboard and Stage II from a number of perspectives. EPA 

believes that the results show refueling control to be a 

cost-effective strategy for reducing VOC emissions and the 

potential cancer risk associated with refueling vapors. 

Moreover, the Agency believes that onboard is more 

desirable than Stage II as a means to attain those 

reductions. 

-78-
P.80 

Proposed Policy Concerning the Role of Stage II 

Controls in Nonattainment Areas 

As described above, the Agency believes that onboard 

is the preferred strategy to limit motor vehicle refueling 

emissions and is proceeding with the accompanying 

regulatory proposal. It should be noted that choosing a 

refueling control strategy presents an unusual issue in 

that one control measure (Stage II) could be employed and 

eventually made obsolete by a more effective system 

(onboard). This introduces the need to evaluate the 

effectiveness over time of requiring essentially redundant 

systems. There are, however, a variety of reasons for 

choosing onboard over Stage II, both as a nationwide 

strategy and as a control strategy for helping 

non-attainment areas ultimately to attain the ozone 

standard. Compared to requiring Stage II controls in 

non-attainment areas only, onboard's advantages include: 

(1) greater long-term emission reduction potential, (2) the 

fact that the consumer does not have to handle new and 

possibly inconvenient refueling equipment, (3) ozone 

reduction benefits in attainment areas, including helping 

to maintain the standard, and (4) nationwide benefits from 

reduced exposure to known and probable carcinogens in 

refueling vapors. 

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P.81 

Congress clearly intended under Section 202 (a)(6) of 

the Clean Air Act that onboard controls potentially could 

be a substitute for requiring Stage II controls. In 

comparing onboard controls to Stage II, EPA believes that 

onboard is the most effective refueling control technology 

and would provide the greatest overall benefits for public 

health and welfare. Thus, EPA believes that onboard would 

be an effective substitute for Stage II controls. 

Accordingly, this proposal to require onboard refueling 

controls is also a proposed determination that the Agency 

will not regard Stage II controls as a "reasonably 

available control measure" within the meaning of Section 

172(b)(2) of the Clean Air Act. The effect of this 

determination would be that EPA would not require that all 

SIPs for ozone non-attainment areas subject to Part D of 

the Act contain Stage II controls as a minimum attainment 

measure. 

Although EPA believes onboard is the preferable 

refueling control approach, the time needed for onboard to 

become effective raises the question of whether refueling 

should also be controlled in the near term by means of 

Stage II implemented as an interim measure in some (or all) 

ozone nonattainment areas. The Agency has examined such a 

dual strategy, as described in Volume 1 of the accompanying 

draft RIA. That analysis examined three hypothetical 

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J 
P.82 

implementation schedules for Stage II, in the context of a 

decision having been made to require onboard controls on 

motor vehicles. The analysis indicated that the value and 

reasonableness of Stage II as an interim measure was 

largely dependent on the speed with which Stage II could be 

implemented in practice. The longer it takes, the more the 

Stage II implementation would overlap that of onboard, and 

thus Stage II as an interim measure would result in rapidly 

diminishing benefits at essentially constant cost. 

An important factor that can affect the reasonableness 

of the interim use of Stage II is the degree of progress in 

the development of Stage II regulations at the State 

level. Stage II is clearly more feasible as an interim 

refueling control measure where it has been installed (or 

is in the process of installation) than in a situation 

where regulations would have to be developed and approved 

under State procedures, and then go through the EPA review 

and approval process prior to implementation. A factor 

related to the speed with which Stage II rules could be 

developed, approved and implemented would be the level of 

controversy surrounding implementation at the local level. 

As discussed earlier in this notice, judging by the 

correspondence received by EPA on the refueling issue, such 

controversy would likely be substantial and the likelihood 

of delays and litigation would be great. 

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P.83 

In light of the above, EPA believes that the decision 

as to whether States must implement Stage II controls for 

the interim period before onboard controls become fully 

effective should depend oh the extent to which States have 

already planned for and implemented Stage II. Accordingly, 

areas where Stage II has already been installed, or is now 

in the process of being installed, must continue to use 

these systems while onboard controls are phased in. In 

these circumstances, the continued use of existing Stage II 

would provide interim environmental benefits at little 

additional cost. Such areas could, however, phase out 

these systems as onboard is phased in. Such changes, of 

course, would need to be incorporated in revisions to the 

applicable SIP. 

Areas that have not begun implementation of Stage II 

controls but whose SIPs contain commitments to do so, 

should proceed with implementation or submit SIP revisions 

providing adequate substitute reductions. In other 

non-attainment areas, interim Stage II controls would 

remain a control measure that States could consider 

including as a part of the area's overall ozone attainment 

strategy. 

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Ill. Key Analytical Issues Affecting EPA's Decision 

The above discussion has attempted to fully set forth 

the analyses and interpretations used by EPA in arriving at 

its decision to propose the onboard control program 

contained in today's notice. The Agency has expended 

considerable effort in its analyses and has considered the 

many issues and uncertainties involved. At the same time, 

EPA is cognizant that there is controversy regarding the 

refueling control issue and is desirous of obtaining the 

fullest degree of public participation in the rulemaking 

process. To assist commenters, this section will again 

review the main options considered by the Agency and then 

present a discussion of the analytical issues which may be 

most important in affecting the outcome of EPA's final 

decision. 

A. Options 

EPA's first main issue concerning refueling was to 

consider whether to control or not control refueling 

emissions. As described earlier in this preamble, the 

Agency believes that control is appropriate. Refueling 

control is important for reducing the generation of ozone 

precursors in non-attainment areas. In addition, today's 

proposal will provide additional benefits in terms of 

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P.85 

cancer incidence reductions and in terms of ozone 

reductions in attainment areas. 

Given the apparent need for refueling control, Agency 

analyses indicate that both onboard and Stage II are cost 

effective approaches. Thus, the second issue facing the 

Agency was to evaluate competing technologies for control. 

As already indicated, the onboard control approach has been 

selected for proposal. Stage II has a potential advantage 

in terms of total cost because it could be applied 

selectively in non-attainment areas only. It also has the 

potential for implementation in the shortest overall 

leadtime (although that advantage is not completely 

clear). However, onboard's greater total cost arises 

largely from its nationwide character, which brings 

additional benefits beyond those offered by Stage II. 

Given a decision to propose onboard controls, there is 

as well an option to propose Stage II control for the short 

term. This approach could provide emission reductions in 

the short term while new cars with onboard controls were 

being phased into the fleet. However, the realization of 

these short term benefits is unclear because of uncertainty 

over the timetable for implementing Stage II. They would 

also be substantially more costly than the benefits of 

either onboard or Stage II alone since they would be short 

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P.86 

term benefits and incremental to onboard. Thus, as 

described earlier in Section II, EPA believes that 

decisions about the use of Stage II in the short term 

should be included in the State Implementation Plan 

development process. It may be as well that additional 

areas will adopt Stage II controls. Any such adoption of 

Stage II by local governments may alter the cost 

effectiveness of a Stage II program compared to onboard 

control. 

A final option to be mentioned concerns possible 

Agency action subsequent to its final rulemaking on today's 

proposal. If the onboard requirement were to be finalized 

with a substantially longer leadtime requirement than 

proposed, EPA would have the option of reviewing the basis 

for its action shortly before the requirement were actually 

implemented to determine if onboard control was still 

appropriate. This might be reasonable given the 

sensitivity of EPA's decision to factors which could change 

in the future. The length of time required to implement 

onbaord control affects its benefit and cost-effectiveness 

compared to Stage II, as does the number of non-attainment 

areas exceeding the air quality standard. In addition, if 

a large number of non-attainment areas were to adopt Stage 

II requirements it could alter the desireability of 

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P.87 

implementing onboard controls. Such a review would be 

conducted approximately one year before the first 

applicable model year. 

B. Analytical Issues 

The proposed choice between onboard and Stage II has 

relied upon an extensive body of analysis which has been 

conducted over a several year period. These analyses are. 

quite complex and by their nature involve a great number of 

projections, judgments and assumptions. Some of these 

areas are generally agreed upon, while others are not. In 

addition, some matters have more impact on the outcome of 

the analyses than others. The following sections review 

assumptions which are either controversial or known by EPA 

to have a significant impact on its analyses. They are 

being described here for the purpose of inviting public 

scrutiny and comment. 

The Agency wishes to caution commenters however, that 

it is quite possible that important analytical issues exist 

which are not identified below. Thus, the Agency 

encourages all parties to carefully review all of its 

analyses and not to confine comments solely to issues 

raised below. 

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P.88 

1. Fuel Volatility 

The impact of fuel volatility on the analysis of 

refueling controls will be reviewed further in Section VI, 

therefore it will not be described in depth here. As 

noted, the primary analyses described in today's proposal 

have been conducted under the assumption of in-use fuels 

being at current ASTM limits (11.5 RVP for summertime 

months in Class C areas). These conditions pose the most 

difficult technical challenge and greatest cost to 

manufacturers. If the Agency finalizes its proposed 

reduction of fuel volatility to 9.0 RVP for Class C areas, 

then manufacturer costs would decline while cost 

effectiveness values would increase. As described above, 

the cost effectiveness of onboard controls would increase 

about 22 percent while Stage II would increase about 13 

percent. 

The single best volatility assumption to use is 

difficult to determine at this point, since EPA has not yet 

finalized its volatility regulation. The presentation in 

today's notice indicates that EPA would expect to proceed 

with onboard controls regardless of whether or not 

volatility is controlled to the levels proposed. At the 

same time, interactions between the two proposals indicate 

that the question of fuel volatility be resolved before 

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P.89 

final action on refueling. Thus, at the time of final 

rulemaking, EPA intends to present its refueling analyses 

under the volatility conditions being promulgated at that 

time. In the meanwhile, commenters are requested to 

consider the effect of varying fuel volatility in their 

comments on this proposal. 

2. Number of Non-Attainment Areas 

Based upon 1982 through 1984 (the latest data for 

which modeling is completed), there are currently 61 urban 

non-attainment areas outside of California. In valuing 

ozone reductions, EPA has credited reductions in all 61 of 

these areas as contributing to solution of the 

non-attainment problem. However, the projections of future 

conditions used in analyzing the effects of control show 

that the number of non-attainment areas may drop 

significantly in the mid-1990s under various possible 

circumstances. For example, the analysis supporting the 

volatility proposal indicates that there may be as few as 

29 non-attainment areas in 1995 with the adoption of both 

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P.90 

volatility control and onboard controls.* Thus, it might 

be argued that ozone reductions should be counted in as few 

as about 30 areas. 

There are several important reasons why the Agency has 

not followed the above approach in its analyses. First, 

the same projections which indicate a decline in the number 

on non-attainment areas to 29 also predict an increase to 

39 again by the year 2010, the period when onboard controls 

will be fully phased in and come to their maximum level of 

control. Thus, 40 areas may be the better estimate. 

Second, and more importantly, a closer look at the modeling 

results indicates that almost none of the modeled areas 

ever gain a substantial margin of compliance against the 

ozone air quality standard. For example, even assuming 

volatility control to 9 RVP and the adoption of onboard 

* The volatility air quality analysis is based upon 

somewhat different assumptions concerning the future 

of stationary source controls than the onboard 

analysis. There is considerable uncertainty about how 

much new VOC control is available from stationary 

sources for the future. The onboard analysis assumes 

no additional stationary source controls, while the 

volatility analysis includes some moderate gains. For 

the same conditions, this causes the onboard analysis 

to predict 4 to 8 more non-attainment areas than the 

volatility analysis. EPA is unsure which of these 

approaches is the more accurate. For this discussion, 

the lower numbers from the volatility analysis are 

being used. 

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P.91 

controls, 58 of the 61 areas modeled remain at or above 

0.11 ppm ozone throughout the period of analysis. This 

represents only about a 12 percent margin below the 0.12 

ppm standard. Such levels are well within the uncertainty 

of EPA's models, which have historically tended to 

overpredict reductions.* Thus, EPA believes that 

reductions in all the modeled areas have value in 

controlling non-attainment conditions. 

There is another reason arguing for considering an 

even larger number of areas than the 61 which EPA has 

identified. Ozone is a broad regional phenomena, not 

confined within the specific geographic boundaries of 

non-attainment areas. The transport of ozone forming 

precursors into non-attainment areas from adjacent 

attainment areas is a significant contributor to 

non-attainment problems. Thus, emissions in areas adjacent 

to the 61 non-attainment areas should also be valued for 

The Agency has consistently stressed the need for 

caution in interpreting modeling results of this 

sort. Year to year meteorology variations can rapidly 

change the number of non-attainment areas when so many 

areas lie very close to the standard. One indication 

of this effect is found in recent data estimating the 

number of non-attainment areas. Based upon 1983 

through 1985 data, the number of non-attainment areas 

appears to have increased from 61 to 65 while modeling 

would predict some decline. 

-90-
P.92 

attainment of the standard (the inherent ability of onboard 

to control such emissions is one of the advantages of this 

technology). EPA is not in a position at this time to 

identify specific areas where this overlap occurs, but 

believes it could be substantial. Comments on estimating 

this effect would be helpful. 

Examination of a few different assumptions about the 

number of non-attainment areas to use indicates that the. 

sensitivity of onboard cost effectiveness to this parameter 

is small for most combinations (Table 6). For example, 

Table 6 indicates that decreasing the number of areas from 

61 to 50 increases the cost effectiveness of onboard 

controls by 9 to 13 percent (depending upon which sets of 

benefits are being valued, see Table 5). Using 40 areas 

represents a 19 to 27 percent increase. 

Table 6 

EFFECT OF VARYING THE NUMBER OF 

NON-ATTAINMENT AREAS ON 

ONBOARD COST EFFECTIVENESS 

N/A Area VOC Cost Effectiveness 

40 Areas 50 Areas 61 Areas >61 Areas 

Benefits Included (28%)* (31%)* (35%)* (50%)* 

N/A Area VOC Only 2800 2400 2200 1500 

N/A Area VOC + BZ 1000 924 850 670 

and C6 GV Incidences 

+ AA VOC Reductions 

Percent of national gasoline consumption 

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P.93 

As noted, there are reasons for considering even more 

than 61 areas in the non-attainment area analysis. Ozone 

is a broad scale regional phenomenon, involving geographic 

transport and ongoing photochemical processes. As the 

technical understanding of ozone formation grows, it 

appears more and more important to consider emission 

controls beyond the specific designated non-attainment 

areas which have historically been analyzed. Here, because 

the exact identification of adjacent areas which might be 

directly involved is difficult, EPA lacks a specific set of 

areas to include. Since non-attainment area benefits are a 

direct function of fuel consumption in the selected areas, 

the Agency has used an alternative based upon an increase 

in the fraction of fuel assumed consumed in non-attainment 

areas. The current 61 areas represent 35 percent of 

nationwide fuel consumption. Assuming an increase in the 

amount of controlled fuel to 50 percent would improve the 

cost effectiveness of onboard by 20 to 30 percent. 

3. Value of Health Benefits and Attainment Area 

Ozone Reductions 

Closely related to the question of how many 

non-attainment areas to use is the question of the value of 

the benefits of reducing cancer incidences and the ozone 

reductions from attainment areas. EPA's analysis examined 

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P.94 

the overall cost effectiveness of onboard assuming values 

of $7.5MM per incidence avoided (for various assumed 

incidence levels) and $250 per ton of VOC reduction in 

attainment areas (which EPA believes is conservative). To 

illustrate the effect of changing the assumed values, some 

alternate values have been considered. The cost per 

incidence avoided (assuming incidences related only to 

benzene plus C6 and above gasoline vapor components) has 

been assumed to range from $3.5MM per incidence avoided to 

as high as $10MM. For potential attainment area benefits, 

a value of $500 per ton has been used in addition to $250 

per ton. 

Table 7 presents the results of this sensitivity 

analysis. From Table 7, it can be seen that the overall 

attainment area VOC cost effectiveness of onboard ranges 

from a low of $150 per ton for the maximum valuation of all 

benefits up to as high as $2200 per ton if no value is 

assigned to either attainment area VOC reductions or 

incidence reductions. 

-93-
P.95 

Table 7 

ONBOARD COST EFFECTIVENESS ($/Mg) 

VOC Value in N/A Areas 

Considering BZ+C6 GV 

Benefit Value Incidence and A/A VOC 

$MM/INCID $/Mg of A/A VOC Reduction Benefits 

0 

3.5 

7.5 

10 

3.5 

7.5 

10 

0 

250 

250 

250 

500 

500 

500 

2200 

1300 

850 

540 

950 

460 

150 

Table 7 does not include the case where all incidences 

attributable to whole gasoline vapors are valued. They 

have been omitted from the table to indicate the 

cost-effective nature of onboard controls even if this more 

controversial source of incidences is excluded. If all gas 

vapors were included, the cost effectiveness of VOC control 

in non-attainment areas would remain negative for most of 

the cases given in Table 7. 

4. In-Use Efficiency of Onboard Controls 

There are three factors affecting the average in-use 

efficiency of onboard systems: the theoretical efficiency, 

the rate of tampering with in-use systems and the rate of 

malmaintenance and defects for in-use systems. For all of 

these areas, the Agency has had to derive appropriate 

values to use based upon indirect data, since onboard 

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P.96 

systems are not yet in routine production. Since the 

overall control efficiency directly affects emission 

reductions to be gained, EPA's approach to these areas is 

important. 

The theoretical efficiency used for EPA's analysis 

corresponds to a 97 percent reduction of uncontrolled 

emissions. By comparison, the reductions required to 

attain the standard of today's proposal are about 99 

percent. The reason for the difference in. values comes 

from the fact that the basic analysis of onboard impacts 

was conducted based upon earlier estimates of onboard 

control efficiency than that eventually embodied in the 

proposed standard. The impacts analyses have not been 

revised to reflect this more recent assessment, largely 

because the impact is small and because any error can be 

considered conservative (i.e., underestimating benefits 

rather than overestimating them). A revised analysis would 

reflect about a two percent improvement in cost 

effectiveness due to the inclusion of this change. EPA's 

analysis for its final rule will reflect the efficiency of 

the standard adopted. 

Tampering rates for onboard systems were derived from 

EPA's experience with evaporative controls. Those 

components of onboard systems directly accessible to the 

operator (vapor lines, purge lines, canisters, etc.) are 

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P.97 

essentially the same as components on current evaporative 

controls. Thus, EPA assumed that tampering with these 

components would occur at the same rate as currently occurs 

on evaporative systems. This tampering rate, on a fleet 

weighted average basis, amounts to 2.8 percent. Assuming 

that tampered systems are completely disabled, there is a 

corresponding 2.8 percent loss in average control 

efficiency. 

EPA's analysis has been conducted based upon the 

assumptions as just described. However, there is reason to 

believe that these assumptions are overly conservative. 

Recent indications from some manufacturers indicate that 

onboard canisters, in at least some applications, will be 

less accessible than evaporative canisters. That is, some 

manufacturers have indicated that they may locate refueling 

canisters in underbody locations or toward the rear of the 

vehicle. The degree to which this will occur is currently 

unclear. However, if such approaches are used, they will 

likely reduce the degree of tampering which occurs. This 

effect has not been estimated, and comments on the 

appropriate approach to this question would be valuable. 

The third factor affecting in-use efficiency 

identified above is the effect of malmaintenance and 

defects (M&D) on emissions. As for tampering rates, EPA 

has relied on experience with evaporative systems to 

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P.98 

estimate the effect of M&D on onboard systems. However, 

the translation of M&D effects from evaporative systems to 

onboard systems is more problematic than tampering, as will 

be described below. 

In its approach, EPA examined M&D data for evaporative 

systems to identify problems which are common to onboard 

systems. For example, problems such as missing gas caps or 

damaged air cleaner gaskets will cause excess evaporative 

emissions to occur, but will not alter the performance of 

onboard systems. These were therefore excluded from the 

onboard analysis. After these exclusions, 7.9 percent of 

the vehicles were found to have M&D problems. Next, using 

test data gathered using commercial (high RVP) fuel, the 

evaporative emissions of these problem vehicles were 

compared to the emissions of problem free vehicles. When 

weighted into the fleet average, this comparison indicated 

a 10.9 percent increase in evaporative emissions was 

occurring due to relevant M&D problems when tested on 

commercial fuel. EPA then applied this percent increase to 

onboard emissions, and related this amount to an equivalent 

loss in control efficiency. That is, the M&D problems 

would increase emissions from onboard equipped cars from 

approximately 0.177 grams per gallon to 0.196 grams per 

gallon (compared to uncontrolled rates of about 5.9 grams 

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P.99 

per gallon). This increase in emission corresponded to a 

change in control efficiency from 97 percent to 96.7 

percent. Being so small, the M&D impact was considered 

negligible and not considered further in the analyses. 

An alternative approach to evaluating M&D impacts has 

been advanced which indicates a greater possible effect. 

Under this alternative approach, rather than computing a 

proportional increase in emissions, M&D vehicles are 

evaluated for an indicated loss in overall evaporative 

control efficiency, and this loss is applied directly to 

the corresponding onboard control efficiency. Operating on 

the most current M&D data for M&D problem rates and 

emission impacts on commercial fuel, this approach has been 

argued to produce a loss in efficiency of three to four 

percent. However, there are several considerations which 

must be addressed before a reasonable estimate can be 

determined using this approach. 

The viability of using a direct transfer of efficiency 

effects depends upon establishing equivalent conditions for 

evaluating impacts for the two technologies. First is the 

need to evaluate the effect of M&D impacts on evaporative 

systems under conditions these systems were designed to 

manage. This means that the M&D impacts must be evaluated 

with 9 RVP fuel. Even problem free vehicles have excess 

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P.1 

emissions when tested on commercial fuel, because the 

evaporative controls are operating beyond their design 

capacity. Thus, a small disablement might increase 

emissions on commercial fuel but have no impact with 9 RVP 

fuel. Since onboard controls will be designed to properly 

operate on whatever commercial fuel is eventually 

established through EPA's volatility proposal, design fuel 

must be used to evaluate evaporative emission effects. 

When results on 9 RVP fuel are considered, the impact 

of M&D problems on evaporative emissions is different. The 

number of vehicles which can be considered to have M&D 

problems is reduced because some of the problem vehicles 

meet the evaporative standard when tested on 9 RVP fuel. 

The absolute amount of excess emissions is also greatly 

decreased. However, emissions from problem free vehicles 

decline even further and, expressed as a percentage change, 

M&D problems have a greater effect at 9 RVP than at 11.5. 

Thus, whereas M& D problems with 11.5 RVP fuel were 

described above as increasing average emissions by 10.9 

percent, at 9 RVP the increase is 30 percent. Using EPA's 

original methodology, this would mean a reduction of 

onboard control efficiency to 96.3 percent. 

To apply this data to an estimated loss of control 

efficiency, the emission levels of the M&D- vehicles on 9 

RVP fuel were compared to expected uncontrolled levels. On 

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P.2 

this basis, the M&D vehicles experienced a loss of control 

of about 35 percent. Averaged over the fleet this amounts 

to about a 2.5 percent loss of efficiency and changes the 

onboard control efficiency to 94.5 percent. 

This value represents an estimate of the maximum 

impact M&D problems could have on onboard systems. 

However, the actual impact is likely to be much less. For 

example, 45 percent of the M&D problems were the result of 

clogged or dirty filters on the evaporative canister. EPA 

expects that most, if not all, onboard systems will use 

closed bottom canisters which do not have such filters. 

Furthermore, there is an essential difference between how 

manufacturers will approach the design of onboard systems 

compared to evaporative systems which is imposed by the 

proposed test procedure. The evaporative procedure tests 

systems under near average conditions while the onboard 

procedure uses a near "worst case" set of conditions. This 

difference will result in onboard systems which have a 

substantial degree of excess capacity for average 

conditions. Thus, partial disablements as represented by 

the M&D problems on evaporative systems will have little or 

no impact on refueling emissions under most conditions. In 

fact, EPA believes it quite reasonable to assume that 

currently known M&D problems will not noticeably affect 

onboard emissions, which was the result of EPA's originalapproach to estimating the effect of this problem. 

-100-
P.3 

There is actually a potential benefit of onboard 

controls related to M&D problems which has yet to be 

quantified. This benefit is the likely elimination of 

evaporative excess emissions caused by M&D problems. Given 

the excess capacity to be designed into onboard systems, 

and given the fact that for most of its driving miles the 

onboard canister will be in a highly purged condition, 

onboard systems will have the ability to absorb M&D effects 

without any corresponding loss of evaporative emissionscontrol. This means that onboard systems could capture 

excess evaporative emissions which are not expected to be 

eliminated by the proposed controls of fuel volatility or 

other changes to the evaporative emission test procedure 

being considered to make it more effective. 

There are other conditions besides M&D problems which 

are currently believed to cause excess evaporative 

emissions which will also be affected by onboard controls. 

In general, they consist of those conditions which result 

in cumulative evaporative emissions which will exceed the 

capacity of even a well designed system. This would 

include such things as vehicles which are not driven 

regularly and undergo repeated diurnal emission loads 

without adequate opportunity to purge the canister. An 

onboard canister would be able to absorb several diurnals 

before emissions breakthrough would occur. A similar 

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P.4 

situation would occur for vehicles driven on mostly short 

trips, again allowing insufficient opportunity for the 

evaporative system to purge. An onboard system would be 

much more tolerant of such deviations than would current 

evaporative systems. The Agency has no quantitative 

estimate of this benefit at present, but believes it could 

be significant. 

The question of the appropriate level of in-use 

efficiency to use for analysis of onboard systems is an 

important matter. The Agency therefore requests comment 

directed at this issue, especially dealing with the points 

discussed above. Any assistance from commenters in 

quantifying these impacts would be most helpful. 

5. Fuel Recovery Credits for Onboard 

The net cost for onboard or Stage II systems includes 

a credit for the fuel value of recovered vapors. For 

onboard this credit is partially offset by the impact of 

the added weight of the onboard hardware on the fuel 

economy of affected vehicles. Some manufacturers have 

argued that when the added weight of the onboard hardware 

is incorporated into new vehicle designs there will be an 

added weight increase through the effect of the onboard 

component weights on the design of other vehicle systems 

(e.g., frame members, springs, engine and drive train 

components, etc.). 

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P.5 

For every pound increase in payload, this argument 

goes, there will be an additional 0.7 pounds added to the 

rest of the vehicle. Thus, the impact of the onboard 

weight must be increased by a factor of 1.7 before 

computing its effect on fuel consumption. Manufacturers 

have also argued that the fuel economy sensitivity of newly 

designed vehicles to changes in weight will be greater than 

that assumed by EPA because the engine displacement would 

be adjusted to maintain a constant driving performance 

characteristic. In addition, additional cost must be 

associated with this added weight and counted as part of 

the onboard control cost. 

EPA's current analysis assumes that the onboard 

hardware on future vehicles will not impact the weight of 

any other parts of new vehicles. It is appropriate in some 

contexts to relate overall vehicle weight to "payload" 

weight, since the design of frames, springs, etc., is 

clearly determined by the required payload. However, in 

the range of four to five pounds of net weight change as 

involved here, the vehicle platform design should not be 

sensitive to such small changes. This is a change 

comparable to the weight of a set of floor mats. There are 

undoubtedly changes of greater magnitude than this made to 

new vehicle components as the vehicle design evolves, and 

EPA does not believe it is reasonable to argue that changes 

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P.6 

are made in, for example, how big the springs will be each 

time this happens. Indeed, this value undoubtedly falls 

well within the range of normal design tolerance and even 

random vehicle to vehicle weight variability. The 

allocation of total vehicle weight to payload item weights 

in this range is more an accounting technique than a 

reflection of actual effects. 

While EPA does not necessarily feel that the weight 

multiplication argument is appropriate in the onboard 

situation because of the small weight changes involved, it 

has done a sensitivity analysis to assess the impact of 

such an assumption. This analysis has been done using a 

weight multiplying factor of 1.3 instead of the 1.7 value 

advanced by some manufacturers and NHTSA. The 1.7 value 

has been developed by NHTSA in connection with the 

development of bumper standards, and used for weight 

changes generally twice or more those being considered 

here. The range of possible values for this parameter 

according to the NHTSA analysis was from 1.3 to 2.0. In 

addition, any effect for light-duty trucks or heavy-duty 

vehicles would be lower than for passenger cars, because 

truck design is more heavily determined by cargo weight 

requirements. 

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P.7 

EPA has made no adjustment to the sensitivity factor 

for fuel economy versus weight change. The changes 

involved are simply too small to be reasonably able to 

impact engine design. For example, the change in 0 to 60 

miles per hour acceleration time associated with the weight 

of onboard controls would amount to an acceleration loss of 

some 0.03 seconds. Such a small change would not even be 

detectable. EPA finds little basis to assume that such 

small impacts would actually affect engine design decisions. 

In determining a cost value to assign to the added 

weight the Agency began with representative costs for steel 

purchased by the automobile industry (20ci/lb), assumed 100 

percent in value added and 26 percent for overhead and 

profit to arrive at a value of 500 per pound. Since the 

effect is being assumed to only affect newly designed 

vehicles, a phase-in schedule was developed assuming a two 

year lag following implementation of the new standards, and 

a fleet turn-over of six years following that. 

Based upon the above assumptions, EPA estimates that 

the overall cost of onboard controls on newly designed 

vehicles would increase by about 10 percent ($1.40). The 

fleet average impact considering the phase-in schedule 

would be to increase the overall onboard cost effectiveness 

by about 5.5 percent. 

-105-
P.8 

There is another factor in the calculation of fuel 

recovery credits which directly affects their overall 

value. That is the assumed price for a gallon of 

gasoline. The value used in EPA's current analysis is 

$1.20, which relates approximately to a crude oil price of 

$30 per barrel. Some forecasts of future crude oil prices 

indicate costs rising above the $30 per barrel level. 

Based upon an increase in the crude oil price to $33 per 

barrel, there would be a 60 per gallon increase in the costof gasoline. If such an increase is applied to the fuel 

recovery credits for onboard, there is a net reduction in 

the onboard cost effectiveness of about three percent. In 

a similar fashion, a 60 per gallon increase in fuel cost 

would improve Stage II cost effectiveness by about three 

percent. 

6. Control of Spillage Emissions 

One source of gasoline vapor emissions associated with 

refueling operations is the spillage of fuel. What might 

generally be considered spillage can come from several 

causes. Spitback spillage can occur when fuel is 

discharged from the fillpipe due to excess pressure buildup 

in the fuel tank vapor space. This can happen near the end 

of a fillup as the tank is nearly full. It can also occur 

earlier when in-use fuel dispensing rates exceed the rates 

-106-
P.9 

that the fillpipe and fuel tank are able to accept. 

Overflow spillage can also occur from the operator's 

attempt to "top off" the fuel tank following automatic 

nozzle shutoff, or if the nozzle malfunctions and fails to 

shut off. Taken as a whole spillage emissions have been 

estimated to represent about 5 percent of total refueling 

emissions and have been considered unchanged by either 

onboard or Stage II controls. 

Although not yet considered, both onboard and Stage II 

equipment are likely to affect spillage. The onboard test 

procedure requirements will require vehicles to be able to 

refuel at the maximum in-use dispensing rate, thus 

eliminating spitback. Finally, given the improved 

fillability this represents, it is likely that reduced 

topping off operations will occur. 

Stage II equipment will not directly bring about the 

elimination of spillage sources. However, since the fuel 

would be contained within the vapor collection boot on the 

Stage II nozzle, spillage would be contained somewhat. 

However, since some of that fuel could subsequently be 

spilled as the operator replaced the nozzle on the 

dispenser, the degree of possible control is difficult to 

estimate. In addition, since the operator cannot visually 

observe the refueling operation, attempts to top off the 

tank may cause increased spillage. 

-107-
P.10 

Overall, it appears that onboard and Stage II will 

help reduce spillage. Onboard appears likely to control 

spillage better than will Stage II, but the Agency has not 

incorporated quantitative estimates of these benefits into 

its cost-effectiveness analysis. Based upon the estimates 

of spillage noted above, however, without any fuel recovery 

credit for the recovered fuel the total control of spillage 

could improve cost effectiveness as much as 5 percent. 

7. Control of Emptying Losses 

Another component of overall refueling emissions is 

that category of emissions known as emptying losses. These 

emissions, which contribute about 5 percent of overall 

refueling emissions, are considered to be generated as part 

of the process in which ambient air is drawn into the 

gasoline underground storage tank to replace the lost 

volume of fuel having been dispensed. The air, as it 

becomes saturated with the gasoline vapors in the 

underground tank, expands slightly. This expansion is then 

presumed to give rise to emissions back out the underground 

tank's vent pipe. 

Emptying losses have not been measured, but have been 

estimated based upon the theoretical considerations just 

outlined. EPA believes that there is reason to believe 

-108-
P.11 

that emptying losses may actually be either much smaller 

than estimated or essentially non-existent. The process of 

drawing out fuel is relatively slow compared to the whole 

volume of the underground tank, and it appears likely that 

air drawn into the tank during the early portion of a 

refueling event will come into equilibrium while the 

refueling operation is continuing. In this event, rather 

than causing an actual release of vapor saturated air, the 

expansion process would merely reduce the amount of 

replacement air needed to be drawn in during the later 

portions of the refueling event. Thus, the only likely 

emissions would come at the very end of the refueling event. 

Beyond this, since refueling is an ongoing process 

wherein multiple refueling events are generally occurring 

in overlapping fashion, even the potential emptying loss 

emissions at the end of one refueling event would tend to 

be eliminated by entrainment demands from other, continuing 

refuelings. 

Thus, it appears that emptying losses may, in fact, be 

very small. In EPA's current analysis, these emissions are 

assumed to be controlled by Stage II, which recirculates 

vapor back from the vehicle fuel tank to the underground 

tank, eliminating air entrainment. Onboard, on the other 

hand, is assumed to have no effect on emptying losses. 

-109-
P.12 

Thus, eliminating the 5 percent of emptying loss emissions 

from the analysis would not change onboard cost 

effectiveness, but would increase the Stage II value about 

5 percent. 

8. Stage II Exemption Levels and Inconvenience Costs 

Both exemption levels and inconvenience costs have 

been discussed earlier in this preamble and their effects 

upon Stage II performance and cost effectiveness 

described. The exemption level used by EPA corresponds to 

approximately the most cost effective level for Stage II. 

Reducing exemptions would increase the fraction of vapors 

captured by Stage II, but would do so at high marginal cost 

effectiveness. For example, VOC reductions from including 

stations between 2,000 and 10,000 gal/mo would cost more 

than nine times those included in EPA's primary analysis 

and would increase the average cost effectiveness of Stage 

II about 55 percent. 

Inconvenience costs have been shown to have a dramatic 

impact upon Stage II cost effectiveness even at a very low 

valuation. At only 100 per refueling event, inconvenience 

costs more than triple the Stage II cost effectiveness. 

While the Agency does not have an exact estimate for actual 

inconvenience costs for Stage II, the use of Stage II 

-110-
P.13 

systems requires the involvement of the public and will 

result in some inconvenience to them. 

9. Coordination of Stage II and EPA's Underground 

Storage Tank Program 

The Agency's recently proposed Underground Storage 

Tank (UST) program could potentially reduce the overall 

cost of a Stage II vapor recovery program. The UST program 

is designed to detect and replace or repair, as needed, 

leaking storage tanks that cause groundwater 

contamination. If the installation of Stage II controls 

were coordinated with underground tank repair or 

replacement, the trenching and paving costs associated with 

Stage II vapor recovery lines potentially could be reduced. 

The Agency's sensitivity analysis of a coordinated 

Stage II/UST program is contained in Volume 1 of the draft 

RIA. In essence, EPA assumed a five-year phase-in period 

for the coordinated program to correspond to the UST 

provisions requiring that all underground storage tank 

systems must be tested for leaks within that time. 

Further, it was assumed that 35 percent of the tanks would 

be found leaking and that immediate corrective action at 

service stations would occur at a relatively linear rate 

over the five-year period. Based on these principle 

assumptions, combining the Stage II program with the UST 

-111-
P.M 

program would improve the cost effectiveness of Stage II by 

about six percent. 

Nonetheless, even this small improvement may be overly 

optimistic. The assumption that 35 percent of the 

underground storage tanks will need repair or replacement 

is a worst-case estimate. Information that is only 

recently becoming available suggests this value is too 

high, perhaps by a factor of three. If the final value is 

closer to 10 percent, the resulting improvement in Stage II 

cost effectiveness would be only two percent. These 

results are also predicated on fully coordinating the two 

programs. In reality, it is doubtful that Stage II 

installation and UST repairs would occur simultaneously in 

every instance. 

Finally, it is important to note that a coordinated 

Stage II/UST program could delay the environmental benefits 

of vapor recovery controls. The Agency's "optimum" 

phase-in schedule for Stage II in non-attainment areas is 

three years, but as discussed above this could be extended 

to five years if coordinated with the UST requirements. 

Then again, even this latter phase-in schedule assumes that 

leak detection and corrective action occur at a relative 

linear rate over the five-year period. This may be 

unrealistic, because many tank owners are - likely to wait 

-112-
P.15 

until the last moment to conduct leak tests. If this is 

the case, a shortage of contractors to perform the 

necessary work may develop, leading to a delay in 

corrective action and a stretch-out of Stage II 

implementation. The longer Stage II implementation takes, 

the more it approaches the onboard phase-in schedule, 

erroding or eliminating the potential short-term emissions 

reduction advantage of Stage II. 

C. Summary of Sensitivity Issues 

The previous section has reviewed a number of issues 

affecting onboard and Stage II cost effectiveness values, 

and attempted to identify the possible impacts associated 

with each. Most of the impacts are small, except for Stage 

II inconvenience costs. Today's proposal is based upon a 

Regulatory Impact Analysis which assumes 61 principal 

non-attainment areas, a fuel volatility of 11.5 RVP, and 

values for the other key parameters as just described. The 

appropriate values for these and other parameters to be 

included in EPA's final Regulatory Impact Analysis may 

significantly affect the results of the final analyses. 

Therefore, the Agency encourages comment on all of these 

factors, along with any others which commenters believe to 

be of importance. Specific areas for comment as identified 

above are: (1) the proper treatment of fuel volatility, 

-113-
P.16 

(2) the appropriate number of non-attainment areas to use, 

(3) the appropriate values for health benefits and 

attainment area ozone reductions, (4) the in-use efficiency 

of onboard controls, (5) treatment of fuel recovery credits 

for onboard, (6) control of spillage emissions, (7) the 

control of emptying losses, (8) Stage II exemption levels 

and inconvenience costs, and (9) the coordination of Stage 

II and EPA's underground storage tank program. Clearly, 

specific quantitative analysis with supporting data will be 

of most use to the Agency in completing its final study. 

IV. Response to Challenges Regarding EPA's Legal Authority 

It has been suggested to EPA that the Administrator is 

obligated to require Stage II controls by regulation for 

all ozone non-attainment areas and, thus, as a practical 

matter, that the Agency has no discretion to choose onboard 

controls over Stage II. This argument is based principally 

on the assumption that Section 172 of the CAA requires the 

SIPs for these areas to include Stage II controls as a 

"reasonably available control measure" (RACM).* EPA does 

* Section 172(b)(2) of the CAA requires that all 

non-attainment area SIPs provide for implementation of 

all "reasonably available control measures as 

expeditiously as practicable" to ensure attainment of 

each primary NAAQS by December 31, 1982 or, in the 

case of ozone and CO, by December 31, 1987. Neither 

the statute nor EPA's implementing regulations 

expressly define RACM and the Agency has broad 

discretion to determine whether and under what 

circumstances any control measure should be considered 

"reasonably available." 

-114-
P.17 

not agree. As discussed in more detail in a separate 

memorandum in the public docket, the Agency believes that 

Congress' intent, as expressed in Section 202(a)(6) of the 

CAA, is that EPA should make a careful, reasoned choice, on 

the merits, between onboard and Stage II controls.[10] 

Thus, the argument that Stage II must be considered RACM 

and that Congress assumed Stage II controls were RACM, is 

inconsistent with the purpose of Section 202(a)(6) and 

would effectively render that section a nullity. The 

Agency does not believe Congress would have intended such a 

result. Moreover, EPA's interpretation is consistent with 

other provisions of the CAA (and its legislative history), 

which indicate that Congress anticipated that the 

Administrator might not require Stage II controls. 

EPA's conclusion is not changed by the fact that 

Section 172 sets December 31, 1987 as the deadline for 

ozone attainment. It does not follow from the existence of 

the deadline that EPA is precluded from thoroughly 

considering Stage II and onboard under Section 202(a)(6) 

and then choosing the more "desirable" technology. Nothing 

in Section 202(a)(6), or any other statutory provision, 

requires that the Administrator base his decision on 

whether to require Stage II or onboard solely or primarily 

on which technology can more easily meet the December 1987 

deadline, or that he sacrifice the potential long-term 

benefits from onboard controls in favor of the greater 

-115-
P.18 

short-term ozone reductions that Stage II might produce. 

In any case, for any non-attainment area not already 

implementing Stage II, the leadtime necessary for 

installation of these controls, although shorter than the 

time needed for onboard to become fully effective, is far 

too long to affect attainment by December 31, 1987. 

Finally, EPA does not agree with the additional 

argument that the Agency itself has previously declared' 

Stage II to be RACM. Although some older EPA information 

and SIP policy documents show that Stage II was considered 

technologically feasible, EPA has never required that a 

State include Stage II as 5RACM in its ozone non-attainment 

SIP as a condition for SIP approval, or otherwise defined 

Stage II to be RACM in any SIP or other rulemaking. 

In summary, EPA is not legally required to declare 

Stage II to be 5RACM in all ozone non-attainment areas and 

is not precluded from proposing onboard control as an 

alternative to Stage II. 

V. Interactions Between the Control of Vehicle Refueling 

Emissions and the Proposed Regulation of Fuel 

Volatility 

This section explores the effect of controlling fuel 

volatility on various aspects of today's proposal, and in 

large part is a summary of the more detailed analysis 

-116-
P.19 

contained in the draft RIA. Such a consideration is 

important because EPA is proposing to control the 

volatility of commercial fuel, as described elsewhere in 

today's Federal Register. As already discussed in Section 

II.D.2. of this notice, the volatility of commercially 

available fuel has risen steadily in the last several years 

and is now significantly higher than that of the fuel used 

in emissions certification testing. The Agency has 

determined that this situation is a primary reason why many 

vehicles exceed the applicable evaporative emission 

standards in customer service. 

In the future EPA intends to have the volatility of 

certification fuel reflect that of in-use fuel. There are 

two basic approaches for ensuring this occurs. The first 

consists of increasing the certification fuel's volatility 

until it reflects the summertime volatility of commercial 

fuel for "Class C" areas of the country as defined by the 

American Society for Testing and Materials. (Class C areas 

are important because the temperature conditions associated 

with the emission test procedures most closely resemble the 

summertime temperatures of these locations.) As described 

earlier, this approach was assumed in the previous analyses 

of refueling controls. Specifically, the analyses used an 

assumed certification fuel RVP of 11.5 psi, rather than the 

current requirement of 9.0 psi (which represented Class C 

area summertime values in the early 1970's). 

-117-
P.20 

As an alternative, the volatility of commercial and 

certification fuels could be regulated to some level below 

that currently found in the marketplace. This is the 

approach taken in the Agency's parallel proposal to 

establish, ultimately, the volatility of commercial 

gasoline in Class C areas at an RVP of 9.0 psi during the 

summer months (i.e., May through September), when the 

majority of ozone NAAQS violations occur. This level 

corresponds to that of current certification fuel, which 

would be maintained at 9.0 psi. The RVP of commercial 

fuels would be uncontrolled by the Federal rules for the 

remainder of the year. In areas other than Class C, RVP 

would be reduced proportionally. If EPA follows this 

approach and acts to regulate fuel volatility in the 

future, the benefits, costs, and cost effectiveness of 

refueling controls would be affected, in addition to the 

specific design of onboard systems. The implications of 

such control on these two general areas are discussed below. 

Turning first to the sensitivity of the refueling 

analysis to volatility control, the relative changes in 

benefits, costs, and cost effectiveness will be illustrated 

for the case where the in-use summertime RVP in Class C 

areas and the RVP of certification fuel is 9.0 psi. The 

sensitivity analysis will first focus on the resulting 

changes in emission reductions, costs, and cost 

effectiveness of the alternative refueling control 

technologies, and then on the estimated cancer incidences. 

-118-
P.21 

The principal effect of changing the volatility level 

is on the gasoline vapor emission factor (i.e., grams of 

vapor per gallon of dispensed fuel). Under the 9.0 RVP 

case, the annual average gasoline refueling emission factor 

is about 11 percent less than for the 11.5 RVP case. This 

change in emission factor has a similar effect on the 

hydrocarbon emission reductions associated with Stage II 

and onboard controls. In each case, the benefits are 

directly proportional to the change in emission factors, so 

that the overall mass of emissions controlled also 

decreases by about 11 percent. Unlike the emission 

reductions, however, the costs of the two control 

technologies are affected differently by changes in the 

emission factor. 

As stated previously, the costs of Stage II controls 

fall into three basic categories: capital costs, operating 

expenses, and a vapor recovery credit. Of these, only the 

vapor recovery credit is affected by changes in the 

gasoline emission factor. Like emission reductions, the 

vapor recovery credit is about 11 percent less for 9.0 RVP 

fuel than for 11.5 RVP fuel. Using this lower vapor 

recovery credit in the analysis raises the overall cost of 

Stage II controls by about 6 percent. 

-119-
P.22 

For onboard, a change in the gasoline emission factor 

affects both the cost of the requisite control hardware and 

the vapor recovery credit. Regarding the hardware, it must 

be remembered that EPA's estimate of onboard control costs 

is incremental to that necessary to control excess 

evaporative emissions. With this in mind, lowering the 

certification fuel's volatility from an RVP of 11.5 psi to 

9.0 psi results in both a smaller, less costly refueling 

emissions storage canister, and a reduction in the cost of 

the requisite vehicle-based evaporative emission controls. 

However, the change associated with the canister is 

significantly smaller than the change in the evaporative 

controls. Therefore, the incremental cost of onboard 

controls over evaporative emission controls with 9.0 RVP 

fuel is about 5 percent higher than the incremental cost of 

onboard over evaporative controls with 11.5 RVP fuel. 

The extent to which the onboard vapor recovery credit 

is affected by a less volatile fuel depends on changes in 

the amount of fuel that is recovered (the gross recovery 

credit) and in the amount of fuel that is used by the 

vehicle to overcome the added weight of the onboard 

system. As was the case for Stage II, the gross recovery 

credit for onboard under the 9.0 RVP case directly relates 

to the change in the emission factors. However, regardless 

of the fuel's volatility, there is no significant change in 

-120-
P.23 

the weight penalty associated with the onboard system. 

Therefore, the net change in the onboard vapor recovery 

credit is larger than indicated by the ratio of the 

emission factors alone. That is, in response to the 11 

percent reduction in the emission factor, the fuel recovery 

credit decreases by 17 percent. Using the higher system 

cost and the lower vapor recovery credit in the analysis 

raises the overall incremental cost of onboard controls by 

about 8 percent. 

Now that the relative changes in emission reductions 

and costs for the two RVP scenarios have been identified, 

the accompanying changes in the respective 

cost-effectiveness values can be discussed. For Stage II, 

the lower emission reductions and higher costs result in 

increasing the cost per megagram of VOC reduced by about 13 

percent for 9.0 RVP fuel compared to 11.5 RVP fuel. For 

onboard, the cost-effectiveness value increases about 22 

percent. These relatively small changes in cost 

effectiveness, however, do not affect the overall 

conclusion (as discussed previously) that refueling 

controls are a reasonable and reasonably cost-effective 

method for reducing ozone precursors in non-attainment 

areas. Neither does the small potential increase in 

onboard's cost effectiveness relative to Stage II controls 

significantly affect EPA's preference for onboard as the 

-121-
P.24 

required control technique, because the overall benefits of 

onboard still make it more desirable. 

In considering the benefits of mitigating the cancer 

risk associated with exposures to refueling emissions, the 

effect of volatility control depends on the type of 

emissions being evaluated: whole gasoline vapors (GV), the 

heavier molecular weight fraction (>CS), or benzene. In 

each case the differences in cancer incidence reductions 

should be approximately proportional to the change in the 

emission factors, but the relative change for each 

pollutant type will be different. For the GV category, 

moving from 11.5 RVP fuel to 9.0 RVP fuel reduces the 

emission factor by about 9 percent as already mentioned. 

This should cause the estimated incidence reductions 

associated with GV exposures to decline by a similar 

percentage. 

The change in emission factors for the ^C6 fraction 

and benzene depends on the methods gasoline refiners use to 

reduce volatility. Generally, EPA believes producers will 

reduce the amount of lighter hydrocarbon compounds in the 

fuel. This will cause the relative percentage of heavier 

compounds to increase somewhat, making the emission factor 

and associated change in incidence reductions associated 

with the _>C6 vapor fraction slightly greater for 9.0 RVP 

-122-
P.25 

fuel than 11.5 RVP fuel. The effect of RVP control on the 

estimated incidences for benzene is difficult to assess. 

If volatility is indeed reduced by decreasing the fraction 

of lighter hydrocarbons,' there also will be a concommitent 

reduction in octane rating. This may necessitate the use 

of octane boosting compounds to maintain desired 

driveability and performance. One method of accomplishing 

octane enhancement is to increase the amount of benzene in 

the fuel. The Agency estimates that, if in-use fuel RVP is 

reduced from 11.5 psi to 9.0 psi, the benzene emission 

factor may increase slightly, causing the relative 

incidence reductions to also increase somewhat. 

Considering all sources of refueling related 

incidences, as well as what is known about likely changes 

in fuel composition, controlling fuel volatility may either 

slightly increase or decrease the cancer incidence 

reductions associated with refueling controls. Neither of 

these changes would appreciably affect the overall results 

of EPA's cancer risk assessment. 

Turning to the interaction between certification fuel 

volatility and onboard designs, some manufacturers have 

suggested that it is impossible to identify the specific 

characteristics of their control systems until a final 

decision is made on the volatility issue. They claim that 

-123-
this prevents them from adequately commenting on an onboard 

proposal. The Agency disagrees with this claim. The form 

and function of onboard systems are well understood as a 

result of the significant prototype development that has 

already occurred. Fuel volatility affects such parameters 

as the exact canister size or purge rate required, but not 

the basic system design. Furthermore, the 11.5 RVP 

certification test fuel assumed in EPA's base analyses 

represents a worst-case situation with respect to the cost 

and feasibility of onboard controls, because, less volatile 

fuels reduce hardware costs and ease the task of 

accommodating higher canister purge rates. Thus, the 

proposal in the volatility rulemaking to retain a lower 

volatility fuel does not significantly affect the decision 

to promulgate refueling controls in general or onboard 

controls in particular. 

Nevertheless, because of the interaction between 

onboard designs and volatility, EPA is publishing both the 

onboard and volatility proposals simultaneously to help 

manufacturers focus their comments. Therefore, although 

comments on both proposals should principally be made in 

the context of 9.0 RVP certification fuel, they should 

reflect the fact that the final RVP of certification fuel 

could be anywhere from 8.0 to 11.5 psi. 

-124-
P.27 

The Agency agrees with the comments made by some 

manufacturers regarding the need to know the exact 

certification fuel volatility before finalizing the design 

of an onboard system for specific applications. Therefore, 

EPA intends to complete action on the proposed volatility 

rulemaking issue before, or in conjunction with, a final 

rulemaking on the onboard refueling control reguirements. 

In summary, the Agency believes that while the 

ultimate level of fuel volatility is relevant, it is not an 

impediment to the proposal to implement onboard refueling 

controls. Nonetheless, to ensure that this issue is fully 

considered in the onboard rulemaking, comments are 

specifically requested on the interaction between 

volatility and all aspects of refueling control. The 

Agency believes adequate information is available to enable 

interested parties to fully consider the effect of various 

volatility levels (i.e., from 8.0 to 11.5 psi) on the 

refueling proposal, and to provide substantial, detailed 

comments. 

-125-
P.28 

VI. Description of the Proposal 

A. Introduction 

As described earlier, today's notice proposes that the 

emissions of gasoline vapors to the atmosphere resulting 

from the refueling of light-duty vehicles, light-duty 

trucks and gasoline-fueled heavy-duty vehicles be limited 

to 0.10 grams of vapor per gallon of fuel dispensed (g/gal) 

(0.026 grams of vapor per liter of fuel dispensed).* The 

exact effective date of the regulations will be determined 

as part of the rulemaking process. However, as discussed 

more fully later in this portion of the Preamble, it would 

not be feasible to begin the requirements earlier than two 

model years after promulgation. 

Associated with the new standards are proposed changes 

to the existing certification protocols to incorporate such 

things as the definition of refueling families and 

allowable maintenance provisions. Test procedures for 

The current emission regulations require that, unless 

exempted, light-duty trucks sold in designated 

high-altitude locations must meet separate 

high-altitude standards. Further, emission standards 

for light-duty vehicles apply at all altitudes, as 

required by Section 202 of the CAA. Therefore, as 

discussed more fully later in this section, a 

refueling standard of 0.10 g/gal is being proposed for 

light-duty trucks at both low and high altitude and 

for light-duty vehicles regardless of elevation. 

-126-
P.29 

determining the levels of refueling emissions are also 

being proposed and are contained in a new subpart of the 

regulations, Subpart C (applicable to both light- and 

heavy-duty vehicles). Also, related changes to evaporative 

and exhaust emissions test procedures are proposed, 

including that canister systems be loaded at least to the 

"breakthrough" point prior to beginning the evaporative 

test sequence, and that heavy-duty gasoline-fueled engine 

exhaust tests be performed with evaporative and refueling 

canisters connected to the engine. 

Also included in the proposed regulatory language is a 

clarified definition of evaporative emissions, as well as 

revised specifications for certification fuel. These 

evaporative emission and certification fuel related changes 

are also being proposed in a separate action on the 

regulation of fuel volatility, which appears elsewhere in 

today's Federal Register. For additional information on 

these revisions, the interested reader should consult the 

volatility proposal. 

The remainder of this section provides a further 

description of today's proposal. Presented first is a 

discussion of the proposed standard and its technological 

feasibility. Next the proposed test procedures are 

summarized. This will be followed by a discussion of 

several matters related to the proposal including such 

-127-
P.30 

things as in-use vehicle testing, vehicle safety, Selective 

Enforcement Audit testing and Nonconformance Penalties. 

Finally, leadtime requirements and projected economic 

impacts of the proposed regulation are discussed. 

More detailed information is available on the topics 

addressed in this section. Background information on the 

development of the proposed test procedure can be found in 

the "Summary and Analysis of Comments on the Recommended 

Practice for the Measurement of Refueling Emissions."[11] 

For information on the technological feasibility of onboard 

controls and the other impacts of the proposal, the reader 

is referred to Volumes 1 and 2 of the draft Regulatory 

Impact Analysis (RIA)[3] and the "Evaluation of Air 

Pollution Regulatory Strategies for Gasoline Marketing 

Industry—Response to Public Comments."[12] All of these 

documents are available in the public docket (A-87-11). 

B. Selection of the Standard 

The technology expected to be used to control 

refueling emissions is similar to that currently used to 

control evaporative emissions. Vapors generated during 

refueling are directed to a canister of activated . carbon 

where they are absorbed on the surface of the carbon 

particles. These vapors are subsequently removed by a 

purging process which draws fresh air over the carbon and 

-128-
P.31 

then feeds the purged vapors to the engine where they are 

burned as fuel. Given the similarity in control 

technology, EPA has followed the same basic philosophy in 

selecting a proposed refueling emissions standard as was 

used to derive the evaporative emission standard. 

The current evaporative hydrocarbon standard for 

light-duty vehicles and light-duty trucks under low 

altitude test conditions (2 grams/test) (40 CFR 86.087-8 

and 86.087-9) is essentially a "zero emissions" standard. 

That is, evaporative control systems can be designed to 

effectively control essentially all of the evaporative 

hydrocarbon emissions from the vehicle. The standard was 

set at 2 grams/test to provide an adequate margin for such 

things as in-use background emissions and testing 

variability.* EPA believes that refueling emission control 

systems can be designed to conform to a similarly stringent 

standard. 

Some automobile manufacturers have commented that 

current evaporative emission control systems are 

EPA is proposing to use the term "evaporative 

emissions" to replace "fuel evaporative emissions" in 

the evaporative emission standards, 40 CFR Part 86, so 

as to clearly identify that the existing evaporative 

regulations encompass background emissions and account 

for testing variability rather than just evaporative 

emissions emanating from fuel sources. The wording 

"fuel" was not in the original standards, but was 

erroneously introduced at a later date. 

-129-
P.32 

functioning poorly in use and are not really capable of the 

high degree of control EPA requires. However, EPA's 

investigation of evaporative emissions has shown that 

excess emissions in the field from well-maintained vehicles 

are due, in part, to the high volatility of in-use fuels or 

to system underdesign, or both.[8] There is no evidence 

that the problem is due to any inherent inadequacies in the 

basic control technology. Properly designed evaporative 

emission control systems have demonstrated the ability to 

control hydrocarbon emissions to extremely low levels, and 

EPA would expect refueling systems to perform in a similar 

fashion. 

Several test programs have been performed which have 

shown that refueling emission control systems can 

effectively control the emissions of refueling vapors in 

practice. EPA tests have demonstrated that more than 98 

percent of the hydrocarbons emitted during the refueling of 

an uncontrolled vehicle can be controlled when the vehicle 

is equipped with an onboard control system.[13] The 

American Petroleum Institute report, "Vehicle Onboard 

Refueling Control" shows the results of refueling tests on 

three vehicles in which refueling emissions were limited to 

less than 0.1 gram per gallon (g/gal)[14]. General Motors 

also recently performed a series of refuelings on a 

passenger car equipped with an onboard system and observed 

emissions ranging from 0.05 to 0.06 g/gal. EPA notes that 

these tests, showing results already capable of meeting the 

-130-
P.33 

proposed standard, were conducted on "first generation" 

onboard systems. System refinements would be expected to 

produce even lower emission levels from future vehicles. 

Currently EPA knows of no test data for refueling 

control systems installed on heavy-duty gasoline vehicles. 

However, since the same control technology would be used 

and since the standard is expressed on a per-gallon basis, 

EPA believes that the required level of control should be 

no more difficult for heavy-duty vehicles than for 

light-duty motor vehicles. Therefore, EPA is proposing the 

same standard for heavy-duty gasoline vehicles as for 

light-duty vehicles and light-duty trucks. 

Since both light-duty vehicles and light-duty trucks 

will have to meet the proposed refueling standard at higher 

elevations, it is also important to consider the effects of 

altitude on refueling emissions. In this regard, the 

Agency is unaware of any test data that characterizes 

refueling emissions at higher elevations. However, there 

does not appear to be any reason that the lower atmospheric 

pressure at high altitude would have a significant adverse 

effect on refueling emissions. 

Actually, in the context of today's onboard and 

volatility proposals, complying with the same numerical 

standard should be less difficult at high altitude than at 

-131-
P.34 

low altitude. This occurs because, in the proposal, the 

RVP of high-altitude certification test fuel may be lower 

than that of the low-altitude test fuel, and a less 

volatile fuel will produce fewer refueling emissions. 

Therefore, EPA believes the proposed refueling standards 

are feasible at both low and high altitudes. 

Based upon its evaluation of the factors described 

above, EPA has selected the proposed 0.10 g/gal standard. 

This level represents a high degree of control (a reduction 

of 98 to 99 percent over baseline levels), but based on 

data available from current generation systems, this level 

appears reasonably attainable. The standard set at this 

level, moreover, allows sufficient leeway to account for 

any measurement variability. 

C. Description of Test Procedures 

In July of 1985, EPA released a draft recommended 

practice for the measurement of refueling emissions from 

motor vehicles.[15] The recommended practice did not 

represent a final EPA determination of a refueling test 

procedure, and was not a rulemaking action, but outlined 

the procedures that, at that time, EPA expected would be 

used as the basis for a refueling test procedure. EPA 

recognized that there were certain deficiencies in the test 

procedure as proposed, and undertook two key steps to 

-132-
P.35 

generate improvements. The first was to solicit public 

comment on the draft procedure. The second was to 

undertake a test program to gain a better understanding of 

the performance of activated carbon canisters in the 

control of refueling emissions. 

The response to the request for public comment was 

extensive and the comments suggested several areas in the 

procedures where improvements were needed. EPA concurred 

with the comments in several areas, the most significant of 

which were: 1) vehicle preconditioning for the refueling 

test, 2) specifications for fuel and vapor temperatures 

required in the refueling test, 3) fuel tank heating 

methods, and 4) the value of a clear line of demarcation 

between the refueling segment of the procedure and other 

segments. 

In response to these comments, and as a result of 

EPA's own testing program, the recommended procedure was 

modified so that the onboard system could be evaluated in a 

single test following an initial preconditioning sequence. 

This revised recommended procedure was presented at a 

public workshop on April 10, 1986 and was generally 

received as a significant improvement which overcame the 

major limitations of the original draft procedure. The 

series of specific changes that made up the described 

modifications resulted in a recommended procedure which 

-133-
P.36 

was greatly shortened from its original form and which was 

not affected by the history of the vehicle prior to 

testing. Numerous other changes of lesser magnitude were 

also made to simplify the recommended procedure and/or 

reduce the possible costs associated with any such vehicle 

testing. These changes generally involved fuel temperature 

specifications and the procedures that would have to be 

followed to achieve the prescribed temperatures. 

The procedure proposed today is essentially that which 

was described at the April 10, 1986 workshop. There have 

been some minor changes and refinements based upon comments 

received since the workshop, but the basic concepts and 

functioning of the procedure are unchanged. The proposed 

procedure has also been broadened in scope to include 

heavy-duty gasoline-fueled vehicles. (A more complete 

understanding of the proposed procedure can be gained from 

a review of the draft regulations themselves as well as 

from Reference 11.) 

1. Overview of Test Procedure 

The purpose of an onboard system for the control of 

refueling emissions is to prevent the escape to the 

atmosphere of those hydrocarbon vapors generated during the 

refueling of the motor vehicle throughout the useful life 

of the vehicle. In order to serve this purpose, the system 

-134-
P.37 

must have hydrocarbon storage capacity sufficient to 

accommodate the vapors generated during a full refueling 

performed at any condition, including near worst case 

conditions. In addition, the system must have a means of 

regeneration capable of purging the collected vapors and 

restoring ample storage capacity between successive 

refuelings. If it is to be effective, any procedure 

designed to test the functioning of an onboard refueling 

emission control system must test both the storage capacity 

and restorative capability of the system. 

Conceptually, the proposed test procedure can be 

broken into three segments (Figure 5). The first two 

segments taken together constitute a preconditioning 

sequence designed to exercise the purging part of the 

system that serves to restore hydrocarbon storage 

capacity. These segments involve first loading the 

hydrocarbon storage medium to an approximation of 

saturation* and then operating the vehicle on a driving 

In the proposed test procedures, EPA has actually 

specified a canister loading procedure which will 

result in canisters being loaded at least to the 

"breakthrough" point. This is a minimum condition and 

systems will be required to pass the test even if 

loaded beyond this point prior to entering the test 

sequence, as might occur, for example, on some in-use 

vehicles. 

-135-
£ 

Integrated System 

Canister Purge, Cyclic Drive 

a. Disconnect Vapor Line to Canister 

b. Drain Fuel Tank 

c. 40% Fueling 

d. Reconnect Vapor Line to Canister 

e. Drive One LA-4 

f. One Hour Hot Soak 

g. Repeat (e) and (f) Twice 

h. Disconnect Vapor Line to Canister 

1. Drain Fuel Tank 

j. 40% Fueling 

k. Reconnect Vapor Line to Canister 

1. Meat 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 SHED to Breakthrough 

Integrated System 

Canister Purge, Continuous Drive 

a. Disconnect Vapor Line to Canister 

b. Drain Fuel Tank 

c. 40% Fueling 

d. Reconnect Vapor Line to Canister 

e. Drive Repeated LA-4s Until Mileage 

Accumulated = Mileage Reguired for 

Purge Equivalent to Cyclic Drive. 

Mileage Accumulation Stops at the 

First Idle Past the Mileage 

Requirement 

1 

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 

Vehicle Cool Down 

Disconnect Line to Canister 

Drain Fuel Tank 

10% Fueling 

Soak Vehicle 6 to 24 Hours 

I 

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) 

OIinOAUL) TL-:UT 1'UCiCKDIIRE l'I.OW CI1AKT 

Figure 5 
P.39 

schedule which would provide sufficient opportunity for a 

properly functioning control system to restore hydrocarbon 

storage capacity corresponding to that normally available 

by the time the fuel tank is essentially empty. The third 

part of the procedure is designed to test the overall 

system storage capacity. It involves refueling the vehicle 

in a SHED* under fuel temperature specifications which 

represent fairly severe conditions for refueling vapor 

generation.** 

In a related matter, EPA is concerned that present 

mixing blower flow rate specifications for SHED testing are 

inappropriate for refueling tests, because of the short 

time intervals associated with the mixing of both 

breakthrough and refueling vapors in the SHED relative to 

time intervals available for mixing of evaporative 

emissions. The Agency is proposing, therefore, that the 

lower flow rates in the current SHED test specifications 

(40 CFR 86.207) no longer be allowed. The increase in 

* SHED is an acronym for Sealed Housing for Evaporative 

Determination, which is an airtight enclosure used to 

measure emissions from the entire vehicle during 

refueling emission tests. This is the same enclosure 

which is currently used for evaporative testing. 

** Activated carbon is not a proportional control 

device. Rather, once it's storage capacity is 

exceeded, further emissions are essentially 

uncontrolled. Therefore, it is necessary to test 

vehicles in a way which will insure the use of designs 

having the capacity to handle nearly all situations. 

-137-
P.40 

** 

Figure 6 

Proposed Test Procedure Flow Diaqram 

--

LOAD CANISTER 

DRIVE 

PRECONDITIONING 

SEQUENCE 

REFUEL IN 

SHED 
P.41 

flow rate is proposed to be achieved by raising the lower 

limits (light and heavy-duty) of the mixing blower flow 

rate specification. 

A more detailed outline of the steps required to 

conduct the refueling test is given in Figure 6. 

Canister Loading. The initial step in the test, as 

identified above, involves loading the vehicle's refueling 

canister(s) with refueling vapors. EPA believes that under 

in-use conditions, it is entirely possible that a vehicle's 

refueling emission control canister could become saturated 

with hydrocarbons. This could occur, for example, if the 

vehicle were not driven regularly and therefore accumulated 

a series of repeated diurnals (fuel tank emissions produced 

by typical diurnal temperature changes), or under driving 

patterns consisting mainly of very short trips with 

inadequate opportunity to purge the canister. It could 

also occur due to high volatility commercial fuels, the use 

of alcohol blend fuels, or abnormally high ambient 

temperatures experienced by the vehicle. EPA would expect 

that under conditions such as represented by the proposed 

preconditioning sequence, such a vehicle's purge system 

would have the ability to quickly restore the hydrocarbon 

storage capacity of the canister. If the vehicle were 

incapable of doing this, additional hydrocarbon loads 

(whether refueling or evaporative) would result in 

•139-
uncontrolled emissions. Therefore, to insure that purge 

systems are sufficient, the proposed test procedure calls 

for a heavy, near-saturation, loading at the start of the 

refueling test. 

The canister loading step, as proposed, consists of 

repeated refuelings in a SHED until, at a minimum, canister 

"breakthrough" occurs, as defined in the procedure 

(basically, the point at which the SHED hydrocarbon 

analyzer detects a sudden rise in hydrocarbon vapors). 

During testing of in-use vehicles this may be performed 

with vapors escaping from the fuel filler neck, or some 

other possible sources, being allowed to vent outside the 

SHED. EPA has received considerable comment on the 

suggested procedure for defining breakthrough, requiring as 

it does the use of a SHED. The possibility has been raised 

that a method for determining breakthrough without the SHED 

may be possible. EPA is sensitive to the issue of resource 

impacts, and agrees that a non-SHED procedure could be 

desirable, but has not yet successfully developed an 

alternative approach. However, recent testing by the 

Agency has indicated that a non-SHED procedure using a 

hydrocarbon probe placed at the canister outlet may be 

viable. If this proves to be the case, then EPA would 

expect to include such an approach in the final rule. 

Comment is therefore requested on this possibility and how 

the procedure might deal with such things as varying 

-140-
P.43 

canister outlet configurations or the control of room air 

currents outside of a SHED. 

Driving Cycles. Following canister loading, the 

vehicle is driven over one of three preconditioning driving 

cycles which are designed to exercise the vehicle's purge 

system. The purpose of all of the driving schedules is the 

same: to allow the vehicle's purge control system to 

restore the storage capacity of the refueling canister to a 

level approximating that which would be available (under 

in-use driving conditions) were the fuel tank to be 

essentially empty and ready to be refueled. Selection of 

the proper cycle to use in any particular case is primarily 

a function of the control system type, as described below. 

In order to understand the functioning of the driving 

cycles, it is first necessary to describe some key aspects 

of the purge operation of a refueling system. With respect 

to purging, there are two broad types of refueling 

systems: integrated and non-integrated. An integrated 

system refers to a system which uses the refueling emission 

control canister to store both the refueling vapors and 

some or all of the evaporative emission load. A 

non-integrated system is one in which the refueling 

canister stores only refueling vapors, and all evaporative 

emissions are handled by a separate canister. 

-141-
P.44 

The functioning of the two system types will be quite 

different under typical driving conditions. For an 

integrated system (which EPA believes will be the preferred 

design), as the vehicle goes through the normal patterns of 

driving, there will be an ongoing process of unloading and 

loading as driving (unloading via purge) alternates with 

parking (loading via hot soaks and diurnal emissions). 

Under repetitive conditions, an equilibrium is quickly 

established between the hot soak and/or diurnal loadings to 

the canister and the amount of vapor purged. Once this 

equilibrium is reached, additional periods of similar 

driving no longer result in an increase in refueling 

storage capacity. (The equilibrium point would, of course, 

change if a different driving pattern were followed. Less 

driving per day would generally produce a lower equilibrium 

capacity point.) 

In contrast, a non-integrated system experiences no 

added loading to the refueling canister between vehicle 

trips. Therefore it will continue to purge the canister to 

lower levels as the vehicle is driven. In this case, 

available refueling capacity continues to increase right up 

until the time the vehicle is refueled and a lower average 

rate of purge than required for integrated systems can be 

used. However, the purge process is highly non-linear, 

with very rapid purge initially, followed by increasingly 

less and less purge as the canister approaches "empty." 

-142-
P.45 

So, even in this case most of the available capacity for 

refueling vapors is generated early in the driving process 

(often referred to as fuel tank "drivedown") following fuel 

tank fillup. 

For vehicles with integrated onboard systems, there 

are two proposed optional driving schedules. The first 

schedule involves operation of the vehicle over a cyclic 

drive sequence which simulates several days of in-use 

driving. For each simulated "day," the vehicle would be 

subjected to three Urban Dynamometer Driving Schedules 

(UDDS's),* each followed by an hour long hot-soak, and a 

single diurnal heat build. As outlined above, operation of 

the vehicle for only a limited number of days restores the 

full capacity for the storage of a refueling load. Based 

upon its modeling analysis, EPA believes that a period of 

three "days" should be sufficient to establish equilibrium 

for nearly all cases. For those cases requiring more 

driving to come to full equilibrium, the impact of 

restricting the conditioning period to three days is 

marginal, involving only a few grams of stored 

The UDDS for light-duty vehicles and trucks, also 

called the LA-4, is a 7.5 mile trip which was designed 

to represent the typical trip an urban commuter 

makes. For heavy-duty vehicles, the UDDS represents 

approximately 5.6 miles of operation at an average 

speed of 18.9 mph. These cycles are found in 4 0 CFR 

Part 86, Appendix I. 

-143-
P.46 

hydrocarbons. On the other hand, every "day" of simulated 

driving represents increased testing time and cost, which 

EPA desires to minimize. Therefore, the Agency is 

proposing three simulated days for the length of this 

preconditioning drive. 

The optional second driving schedule for vehicles with 

integrated systems would involve much less driving time 

than would be needed for the cyclic drive. This proposed, 

schedule is a short continuous drive designed to purge the 

canister to the same level as attained by the cyclic drive 

without going through the actual load/purge cyclic 

process. It is an abbreviated schedule designed primarily 

to reduce testing time compared to the full cyclic drive. 

The actual length of the drive would be determined by 

testing to establish equivalence to the cyclic drive, and 

would be established uniquely for each refueling family 

during the certification process. EPA's analysis indicates 

that most systems should be properly purged with only five 

to twenty-five miles of continuous UDDS driving. 

The short continuous drive provides a means of testing 

the restorative capacity of the refueling system with a 

greatly abbreviated procedure. Because of this, EPA 

expects to use the continuous drive for most of its testing 

work. EPA also expects that manufacturers would use the 

abbreviated procedure wherever possible to minimize testing 

-144-
P.47 

resources. The Agency recognizes that there is some added 

burden for manufacturers in having to conduct the cyclic 

procedure initially in order to develop the appropriate 

continuous drive mileage, but once this is done for a 

particular configuration, the abbreviated cycle could be 

used for subsequent repetitive tests (e.g., on durability 

vehicles). 

In spite of its usefulness as an abbreviated 

preconditioning cycle, the continuous drive has some 

limitations. The abbreviated procedure does not physically 

demonstrate that the system has the ability to sufficiently 

purge the canister when hot soak and diurnal loads are 

included. Rather, this procedure assumes the control 

system has been designed such that this would be the case 

were the cyclic drive to be used. Therefore, although the 

continuous drive would be the procedure of choice for most 

routine testing, the cyclic drive could be used should EPA 

desire to perform confirmatory testing and to more fully 

exercise the onboard system. Thus, all vehicles would have 

to be designed to be able to meet refueling emissions 

standards after following either driving schedule and EPA 

could choose to confirmatory test any vehicle using the 

cyclic drive or the short continuous drive. 

-145-
P.48 

Both the cyclic and the short continuous drives just 

described are intended for vehicles using integrated 

refueling control systems. The third driving sequence is 

intended for vehicles with non-integrated refueling and 

evaporative control systems. Because non-integrated 

systems continue to gain purge capacity while being driven, 

it is difficult to completely test the restorative 

capability of the system using an abbreviated driving 

schedule. Therefore, in today's notice, EPA proposes a 

continuous drive which involves a repetitive series of 

UDDS's which would use fuel equivalent to approximately 85 

percent of the vehicle's nominal tank capacity. By 

actually driving out the tank of fuel, a non-integrated 

system will clearly be prepared for a full refueling. 

Since non-integrated systems are not affected by diurnal or 

hot soak loadings, the driving schedule is a continuous 

process. 

A full drive-down requirement such as this is 

obviously quite resource-intensive and EPA would like to 

develop a suitable alternative. One alternative which 

appears promising is based upon the non-linear nature of 

the purging process. Because of this non-linearity, it 

appears that a partial drive-down of perhaps 30 to 40 

percent of tank volume would generate most of the refueling 

control capacity which the vehicle was capable of 

producing. In such a case, it would be possible to perform 

•146-
P.49 

a refueling test which would measure nearly all the 

expected emissions after only a partial drive-down. While 

such a test would not directly verify full refueling 

capacity, test points could be derived from an engineering 

analysis which would clearly indicate that satisfactory 

performance at that intermediate level would be expected to 

result in full performance on an essentially empty tank. 

Based, as it would be, on a less than full verification of 

system performance, EPA would treat such an approach 

similarly to the short continuous drive for integrated 

systems. That is, the partial drive-down would be an 

optional abbreviated test, with all vehicles being required 

to be able to pass the full drive-down if so required by 

EPA. EPA specifically requests comment on this concept as 

an alternative driving sequence for vehicles with 

non-integrated systems. If after further analysis, such a 

concept is found to be valid, EPA could choose to include 

such a provision in the final rulemaking. 

Final SHED Refueling Procedure. As stated earlier, 

following the performance of the appropriate driving 

schedule, the vehicle would be fueled in a SHED under 

specific conditions of fuel temperature and volatility. 

The refueling would be accomplished with a typical nozzle 

inserted through a boot in the wall of the SHED. The test 

would begin with residual fuel in the tank corresponding to 

10 percent of tank capacity; refueling would proceed until 

-147-
P.50 

automatic nozzle shutoff. For a valid test, the tank would 

have be fueled to at least 95 percent of capacity. The 

fueling operation would be re-started if automatic shutoff 

occurred before this point. 

Based on a variety of government and industry test 

programs, it has been shown that the temperature and 

volatility of the dispensed and residual tank fuels during 

the refueling largely determine the uncontrolled refueling 

emission rate. In order to insure the maximum degree of 

control, these temperatures have been selected such that 

refueling at the proposed conditions results in refueling 

emissions of greater magnitude than are generated in most 

actual in-use refuelings. 

Although EPA is reasonably confident that the proposed 

conditions would adequately ensure that a system is capable 

of meeting the proposed refueling standard under most 

conditions, it is difficult to determine exactly what 

percentage of all refueling situations will be fully 

controlled. Data describing the distribution of tank and 

dispensed fuel temperatures during summertime conditions 

formed the original basis for EPA's parameter 

selection.[15] Based upon consideration of that data 

alone, the test conditions may appear somewhat severe. 

However, there are other variables affecting the control 

system performance that are not so easily quantified. One 

-148-
P.51 

of these is vehicle driving patterns. The proposed 

preconditioning cycles for integrated systems described 

earlier are based upon a driving pattern of three trips per 

day. For those vehicles driving fewer trips, canister 

purging can be significantly reduced, thereby reducing 

effective refueling capacity. Another important variable 

is the degree to which hot soak and diurnal evaporative 

loadings during ozone non-attainment days may exceed the 

nominal values used in the preconditioning sequence. 

Increased loadings of these sorts would . also reduce 

available refueling capacity, and do it precisely at those 

times when it is most needed. That is why EPA proposes to 

require systems to be designed to function effectively 

regardless of these and other variables. 

Overall, EPA believes that the preconditioning and 

refueling test condition requirements as proposed will 

ensure control system designs capable of adequate control 

over nearly all expected refueling events. There may be 

some combinations of in-use conditions where refueling 

emissions may not be fully controlled. The Agency believes 

that those conditions will be sufficiently infrequent as to 

have no significant impact on overall compliance with the 

proposed standard, or on the level of vapor emission 

reduction projected under the proposed standard. 

-149-
P.52 

2. Fuel Nozzle Design 

During the development of the recommended refueling 

test procedures, the topic of differences between fuel 

nozzles produced by different manufacturers has 

occasionally been raised. For example, Ford has performed 

a limited number of uncontrolled refueling tests using 

nozzles of various designs and has suggested that nozzle 

geometry can strongly influence refueling emissions. In 

fact. Ford claims that nozzle dimensions can affect both 

the uncontrolled emission rate and the rate at which a 

particular fillneck design will permit refueling. Because 

of these effects Ford has strongly urged EPA to specify a 

standard nozzle for use in the refueling test. [16] 

EPA is also concerned about the impact that nozzle 

geometry may have on refueling emissions, but has little 

data at present with which to evaluate these claims. If it 

were true that nozzle geometry can substantially affect the 

performance of refueling systems, then a standardized 

design would be indicated. In EPA's view, if this were the 

case, such standardization would have to be applied both to 

test equipment and to in-use nozzles. Otherwise, refueling 

system performance would suffer in practice. 

-150-
P.53 

EPA requests comments on the need for standardized 

nozzle geometry. Particularly, EPA requests the submission 

of test data demonstrating the degree of sensitivity 

refueling controls may show to nozzle variants, as well as 

specification of which nozzle design parameters would need 

to be standardized. The Agency believes that if such 

geometry standards are needed, the most likely design 

parameters involved would include total length, spout 

bending angle, length of spout straight section, and 

automatic shut-off port location. Commenters should 

address the standardization of these and any other 

parameters of principal concern. This should also be 

accompanied by an analysis clearly demonstrating why it 

would be better to standardize nozzle geometry than to 

require refueling designs which are less sensitive to these 

factors. If the comments substantiate the need for nozzle 

standards, EPA may include them in the final rulemaking on 

today's proposal. 

3. Related Changes to Existing Test Procedures 

In addition to the regulations governing the 

measurement of refueling emissions, EPA is proposing 

several changes in the current Federal Test Procedure as 

part of today's notice. The most significant changes will 

be discussed later in this section and involve the 

preconditioning of emission control canisters prior to 

-151-
P.54 

evaporative emission compliance testing, the inclusion of 

canisters in heavy-duty gasoline-fueled engine emissions 

testing and the manner in which canisters are 

preconditioned for fuel economy testing. Other revisions 

include changes to the research octane number, aromatic 

content, sulfur content, and distillation characteristics 

of certification fuel. In addition, the oxygen content of 

certification fuel is being specified for the first time. 

These changes, as well as those just described, are also 

being proposed in EPA's action to control the volatility of 

commercial motor vehicle fuel. That notice appears 

elsewhere in today's Federal Register and should be 

consulted by the reader for more detail on the evaporative 

and certification fuel related revisions. 

There are also other minor, technical changes to the 

test procedure being proposed as part of today's notice, in 

order to update the procedure and make it more consistent 

with actual practice. The reader who wishes a full 

understanding of the details of these technical changes 

should consult the appendix and draft regulations 

accompanying today's notice. 

It has been EPA's position that evaporative emission 

control systems should be designed to work effectively and 

maintain their level of control under in-use operating 

conditions. It also has been EPA's position that 

evaporative emission control systems should be able to 

-152-
P.55 

quickly recover their hydrocarbon storage capacity after 

experiencing any of the various conditions that might occur 

in-use. In particular, the Agency described its intent 

that evaporative emission control systems have the 

capability to restore hydrocarbon storage capacity with a 

single UDDS (even if the canister is saturated at the start 

of the test sequence) in EPA Advisory Circular 50A. 

Nonetheless, some vehicle manufacturers continue to express 

confusion on this issue. 

In order to clarify this matter, and avoid a similar 

problem regarding the capability of refueling emission 

control systems, the Agency is proposing a requirement to 

load evaporative and refueling control canisters at least 

to the breakthrough point prior to the FTP preconditioning 

UDDS. For evaporative emissions testing, breakthrough 

would be defined by the same procedure as developed for the 

refueling test. This change would apply to both light- and 

heavy-duty vehicles. 

A closely related change is being proposed for the 

testing of heavy-duty gasoline engines. In the current 

Federal Test Procedure for heavy-duty engines, there is no 

requirement for evaporative emission control systems to be 

in operation during the performance of the exhaust emission 

test sequence. This means that any evaporative hydrocarbon 

loads that would be sent to the engine during normal 

operations are not sent to the engine during the exhaust 

-153-
P.56 

test. Therefore, any impacts that the evaporative 

hydrocarbons might have on exhaust emissions are overlooked 

in the current test procedure. EPA does not believe that 

this situation is appropriate for either evaporative or 

refueling control systems. Therefore, EPA is proposing 

that prior to the heavy-duty engine test, the vehicle's 

evaporative and refueling control canister(s) be attached 

to the engine. Loading of the canister(s) will correspond 

to a point equivalent to the loading which would exist at 

the end of the diurnal breathing loss test. This change 

will insure that manufacturers focus appropriate attention 

on eliminating any exhaust impacts of the control systems, 

as is already required by the light-duty procedures after 

the 1990 model year. 

Other proposed change(s) would affect the test 

procedures used for determining light-duty fuel economy 

values, which are ultimately used in calculating a 

manufacturer's corporate average fuel economy (CAFE). 

Because it has been argued that the addition of onboard 

control systems could affect vehicle fuel economy 

measurements, EPA is proposing to give the manufacturer the 

choice of performing the fuel economy test with or without 

the step of loading the canister beforehand. The 

manufacturer would be allowed to pick the procedure which 

it desires, with the condition that all fuel economy tests 

with unloaded canisters would be subject to prior approval 

by the Administrator. 

-154-
P.57 

The Agency is considering other CAFE-related changes. 

First, rather than the manufacturer performing a duplicate 

test with an unloaded canister for fuel economy purposes 

only, which could increase testing costs, EPA might include 

a CAFE adjustment to account for the fuel economy effect of 

testing with a loaded canister. Second, EPA is 

contemplating whether or not a CAFE credit should be 

developed representing the expected recovery and use of 

refueling vapors. Comments are specifically solicited on 

the appropriateness of such a CAFE adjustment and credit, 

as well as the methodologies for their determination. In 

addition, EPA invites comments on other alternatives that 

would avoid double testing for fuel economy purposes. 

The Agency would also like to acknowledge that if the 

volatility of test fuel is changed from the currently 

specified RVP of 9.0 psi, an option which has been 

evaluated as part of the volatility proposal, then 

appropriate revisions to the CAFE determination procedures 

would be made as part of the final rulemaking on volatility. 

4. Testing In-Use Vehicles 

EPA has always intended for motor vehicle emission 

standards to be met in-use. That is, EPA expects that 

properly maintained and used vehicles will comply with 

applicable emission standards in-use if tested at any 

-155-
P.58 

mileage point up to their full useful life. Vehicles 

would, of course, also be expected to comply with refueling 

emissions standards in-use and the procedures described in 

today's proposal were designed for use in both 

certification and in-use testing. During the development 

of the proposed procedures, careful consideration has been 

given to the implications of testing in-use vehicles. EPA 

has also consulted extensively with industry on this topic 

and believes that the procedures proposed today will test 

in-use vehicles appropriately. 

One important concern raised by manufacturers about 

testing in-use vehicles is that the condition of the 

vehicle (especially the activated carbon canisters) is 

unknown before the vehicle begins the test sequence. It is 

important that the procedure be able to accurately assess 

the performance of the control system regardless of its 

state prior to testing. The proposed refueling test 

procedure has been designed so that this is the case. 

As described above, the first step in the refueling 

test is that of loading the refueling canister at least to 

the breakthrough point. Thus, for all those vehicles 

presented for testing with canister loading at some point 

below the breakthrough level, the procedure results in a 

standardized condition at the beginning of. testing. For 

those vehicles beginning the sequence with their canisters 

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already loaded past the breakthrough point, the situation 

would be somewhat different. Two observations apply to 

this situation. First, it is EPA's position that the 

vehicle purge system should be able to fully recover from 

such a condition without added preconditioning. The 

breakthrough loading sequence is intended only as a minimum 

loading requirement. If a significant number of vehicles 

were actually operating with saturated canisters it would 

be as a consequence of the manufacturer's system design. 

In such a case, EPA would require that these vehicles pass 

the test as received. 

The second observation on this point is that all the 

information available to EPA indicates that a saturated 

refueling canister will present no significant liability 

for a properly designed system because such heavily loaded 

canisters purge extremely rapidly on the proposed 

preconditioning cycles. Following the preconditioning 

drive sequences, it would be difficult to distinguish 

between a canister which began the test saturated and one 

which was only loaded to breakthrough. It should also be 

noted that EPA believes that the preconditioning sequence 

effectively eliminates any unanticipated effects on the 

refueling system due to such causes as the use of 

non-standard fuels. 

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Another facet of in-use testing involves those 

vehicles for which optional preconditioning cycles exist. 

The Agency wishes to make it clear that when optional 

preconditioning cycles are available, the option selected 

by EPA for certification testing does not dictate the 

option to be used to test for in-use compliance; moreover, 

the vehicle must be able to pass using any applicable 

optional cycles both during certification and in-use. 

Similarly, failure of a vehicle using one preconditioning 

cycle would not entitle the manufacturer to ask for testing 

using another cycle. 

D. Selective Enforcement Audits 

During the development of the recommended test 

procedure for refueling emissions, two minor issues were 

raised which may need to be addressed in Selective 

Enforcement Audit (SEA) test procedures* for refueling 

emissions. These potential issues are related to the fact 

that SEA involves the testing of newly-built motor 

vehicles, and for that reason they are unique to the SEA 

program. 

SEA testing refers to testing under Section 206(b) of 

the CAA and 40 CFR Part 86 of a statistical sample of 

assembly-line vehicles to ensure that vehicles being 

produced do in fact conform with emission standards 

and the terms of the applicable certificate. 

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The first issue regards a possible influence of new 

vehicle background evaporative emissions (i.e., hydrocarbon 

emissions from such things as the fresh paint on a new 

vehicle which has not yet fully cured) on the refueling 

emissions measurement. EPA understands why non-fuel 

background emissions are significant in evaporative 

emissions testing for SEA purposes and consequently EPA 

does not normally conduct SEA testing for evaporative 

emissions. However, EPA does not believe that background 

emissions will improperly affect refueling loss 

measurements during SEA testing.* Refueling emission 

measurements have a duration of less than five minutes, so 

the actual time for background evaporative losses to occur 

is very short. Also, refueling measurements are taken at 

an ambient temperature of approximately 80°F, so fuel and 

non-fuel evaporative emissions will not be increased by 

heating of the vehicle fuel tank, engine or other 

subsystems, as occurs during the usual evaporative 

emissions testing. Because of those factors, it is 

reasonable to expect that background emissions will have 

little or no impact on the measurement of refueling 

emissions, and EPA does not believe that provisions to 

In addition, under the proposed refueling standard no 

attempt will be made to distinguish other evaporative 

emissions from those generated by refueling. As already 

noted, the standard is intended to include background 

emissions. 

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address the effects of background emissions during SEA 

refueling testing are necessary. 

However, EPA is open to comment on this issue and 

specifically requests any available data suggesting that 

non-fuel background emissions from newly built vehicles 

would be significant in the refueling test procedure 

proposed by EPA. Since the proposed refueling standard is 

intended to include whatever normal background emissions 

occur for in-use vehicles, data supporting the impact of 

background emissions during SEA testing must demonstrate 

that new vehicle background emissions significantly exceed 

in-use vehicle background emissions. 

If evidence exists that background emissions are 

significant, EPA proposes to incorporate an additional 

procedure into the SEA refueling emissions test 

procedures. This procedure would provide for the 

measurement of new vehicle background emissions and 

subtract them from the refueling emissions measurement. In 

general, the proposed procedure is as follows: 

1. Place the vehicle in the SHED immediately prior 

to the refueling emissions measurement sequence of the 

refueling test. 

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2. Seal the SHED and measure the ambient 

concentration of hydrocarbons in the SHED. 

3. After a 10 minute period take another 

measurement of the SHED ambient hydrocarbon concentration, 

calculate the total grams of hydrocarbon emitted (final 

minus initial measurement) and divide by 10 to calculate a 

per-minute emission rate. 

4. Perform the refueling emissions measurement as 

described in the refueling test procedure,, recording the 

duration of the refueling measurement process, rounded to 

the nearest minute. 

5. Multiply the background emission rate 

(determined in step 3) by the number of minutes obtained in 

step 4, and subtract this number from the total grams of 

emissions calculated from the refueling emissions 

measurement to obtain a corrected value for total refueling 

emissions. 

The second issue pertains to the condition of the 

refueling/evaporative emission canister(s) prior to SEA 

testing. It is generally accepted that activated carbon 

canisters require a number of hydrocarbon load and purge 

cycles (aging) to attain a stabilized condition. During 

this cycling, the canister's capacity to retain 

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hydrocarbons is reduced from its virgin (new canister) 

level to some lower stabilized level generally referred to 

as the working capacity. This loss in capacity is commonly 

known as the "heel". To help account for any large 

difference that may exist between an unused canister and a 

somewhat used canister, EPA proposes that 

refueling/evaporative emission canister(s) of SEA vehicles 

be aged through a bench procedure, prior to being tested 

for refueling emissions. The proposed procedure for aging 

the canister is detailed in the accompanying draft 

regulations. The Agency wants to make it clear, however, 

that this procedure is meant only to approximate some 

degree of canister aging. It is not known to what extent 

it simulates actual real-world canister stabilization or 

deterioration with age. Therefore, while proposed for SEA 

testing, the bench aging process is inappropriate for the 

purpose of certification testing or the development of 

deterioration factors. 

The Agency is interested in obtaining comments 

addressing the appropriateness of performing SEA refueling 

emission tests without stabilizing refueling canisters on 

the vehicles, other possible procedures or requirements for 

cycling (aging) canisters, and the level to which canisters 

should be aged. 

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E. Nonconformance Penalties (NCPs) 

In the regulations governing NCPs (40 CFR 86.1103-87), 

EPA specifies the criteria which must be met before an NCP 

will be made available for a new emission standard 

applicable to any subclass of heavy-duty vehicles (i.e., 

vehicles with a GVWR in excess of 6000 lbs). As described 

in those regulations, an NCP may be established for a new 

emission standard if substantial work will be required to 

meet the new standard and a technological laggard is likely 

to exist. Substantial work means the application of 

technology not previously used in a vehicle class or 

subclass or the significant modification of existing 

technology or design parameters. 

While onboard systems have not been used to control 

refueling emissions on heavy-duty vehicles, EPA does not 

believe that an onboard requirement constitutes substantial 

work as defined in the NCP regulations nor does EPA believe 

that a technological laggard will exist. The fundamental 

design of an onboard control system is basically an 

extension of existing evaporative emission control 

technology rather than the application of new technology. 

EPA expects manufacturers to use activated carbon for 

storage of refueling vapors and air stripping for 

regeneration, just as is now used in evaporative emission 

control systems on heavy-duty gasoline vehicles. Purge 

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systems would have to be refined to handle increased 

hydrocarbon loads, but these improvements would not involve 

the application of new technology, especially given the 

manufacturers' plans to incorporate fuel injection and 

feedback control systems to upgrade the performance of 

these vehicles. 

While there may be some subjective disagreement on 

whether or not "substantial work" will be involved in 

meeting the standard, EPA believes all the manufacturers of 

these vehicles will be able to comply with the standard and 

that no technological laggard will exist. EPA recognizes 

that effort will be required to equip heavy-duty vehicles 

with onboard control systems, but the control technology 

required is well defined and available to all affected 

manufacturers. 

In addition, the NCP regulations also permit 

consideration of NCPs for other emission standards, for 

which NCPs are not already provided, if the standards 

become more difficult to meet as a result of a new 

standard. However, as is discussed in the technological 

feasibility portions of the support documents, EPA does not 

believe that manufacturers will encounter significant 

additional difficulty in maintaining compliance with 

current standards as a result of the proposed onboard 

standard. "Substantial work" will not be reguired and no 

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technological laggards are expected. Therefore, EPA 

proposes not to make additional NCP's available for exhaust 

or evaporative emission standards as a result of any new 

onboard standard. 

Given the information currently available regarding 

onboard control technology, EPA proposes not to make NCPs 

available for the refueling emissions standard. However, 

EPA may change this position based on information presented 

in the comments. If NCPs for refueling are ultimately 

proposed, they will be addressed in a rulemaking action 

separate from the refueling emission standard. However, 

the parameter values needed to calculate any proposed 

penalty rates and the upper limit analyses may be based on 

information used in the final rulemaking analysis for 

refueling controls. 

F. Changes to Certification Protocols 

In addition to new emission standards and test 

procedures for refueling, this notice proposes a number of 

revisions to the certification protocols in Subpart A. 

These revisions are necessary to integrate the proposed 

refueling control program into the existing protocols for 

exhaust and evaporative emission certification. In 

general, the certification requirements for refueling 

emissions are quite similar to the existing evaporative 

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emissions requirements. However, some new provisions and 

changes to existing provisions were required by the 

addition of the refueling standards. The most significant 

revisions to Subpart A are as follows: 

Section 86.090-21 (Application for certification) 

requires manufacturers to describe the method used to 

determine refueling emission deterioration factors for 

their refueling emission families. These requirements are 

similar to those currently governing evaporative emissions 

deterioration factor determination. Additionally, however, 

manufacturers are required to state in their application 

the length of the continuous drivedown necessary to purge 

the refueling canister(s) to the appropriate level required 

by the test procedure. 

Section 86.090-23 (Required data) data reguirements 

for refueling certification for light-duty vehicles and 

trucks are similar to current exhaust and evaporative 

emissions data requirements. Similarly, the requirements 

for heavy-duty manufacturers are similar to the current 

heavy-duty evaporative emissions requirements. (Note that 

Subpart C now requires that a loaded evaporative/refueling 

canister be attached to the engine during exhaust emission 

testing.) 

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Section 86.090-24 (Test vehicles and engines) contains 

criteria for determining refueling families and refueling 

control systems. Many of these criteria are the same as 

those for evaporative family and control system 

determination, due to basic system design similarities. 

However, other criteria such as degree of integration with 

the evaporative control system, type of fillpipe seal and 

fill limiter are unique to refueling systems. Therefore, a 

refueling family may not necessarily cover the same portion 

of a manufacturer's product line as an evaporative family. 

The same refueling family/system criteria are applicable to 

both light-duty and heavy-duty vehicles. Suggested 

criteria for identifying worst-case emitters within a given 

family/system combination for certification purposes can be 

found in a memorandum entitled "Refueling Configuration 

Criteria" in the public docket. 

Section 86.090-25 (Maintenance) defines refueling 

emission components as critical emission-related components 

and prescribes full-life maintenance intervals for such 

items as fillpipe seals, vapor storage canisters, and purge 

system hardware. 

Section 86.090-28 (Compliance with standards) provides 

that refueling emission deterioration factors shall be 

additive. 

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Section 86.090-35 (Labeling) requires that refueling 

families be labeled as such and that secondary 

manufacturers must add vapor storage capacity in proportion 

to any added fuel tank volume. Furthermore, it requires 

them to certify that any additional fuel tank capacity 

beyond the maximum specified for a refueling family will 

not cause that family to exceed the applicable exhaust, 

evaporative or refueling standards. 

Although the major changes in the regulations have 

been summarized above, the interested reader is urged to 

consult the appendix to this notice and the proposed 

amendments to Subpart A in their entirety for a complete 

understanding of the technical effects of the proposed new 

refueling standards on the test procedures. The Agency 

invites comments on all aspects of the proposed revisions. 

In particular, EPA requests that each manufacturer submit a 

projection of the likely number of refueling families and 

refueling control systems that would exist under the 

proposed criteria. 

G. In-Use Dispensing Rate/Nozzle Geometry Standards 

As part of this action, beginning in September 1989, 

EPA is proposing to limit the in-use dispensing rate of 

gasoline to 10 gallons per minute (gpm). Furthermore, as 

discussed earlier in Section VI.C.2. of this notice, EPA is 

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seeking comment on the need to standardize fuel nozzle 

spout design geometries. As described below, EPA is 

considering these actions to insure compatibility between 

in-use operating conditions for onboard systems and those 

under which the systems will be certified. 

The fuel dispensing rate during refueling operations 

affects the design of onboard controls through such 

parameters as fillpipe capacity, fillneck seal performance, 

excess air entrainment, vapor line sizing, canister size 

and geometry, the generation of nuisance shutoffs and fuel 

spitback. This topic has been raised to EPA by 

manufacturers in comments on the development of the 

suggested refueling test procedure discussed earlier.[14] 

Therefore, in developing its proposed certification test 

procedures, EPA conducted an analysis of prevailing in-use 

dispensing rates. The proposed dispensing rate for test 

conditions (10 gpm) is based upon the highest dispensing 

rates presently found at most gasoline dispensers. 

However, as vehicles capable of accepting fuel at the 

current maximum flow rates become more prevalent in use, 

gasoline marketing pressures for increased throughput 

(i.e., to increase sales volume) would be expected to lead 

to increased in-use dispensing rates up to the point where 

customer complaints begin to arise due to spitback and 

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other spillage.* (The likelihood of this occurring has been 

acknowledged by gasoline marketers in discussions with 

EPA). Thus, in order to maintain the full effectiveness of 

onboard systems in the future, EPA believes it is important 

to also insure that in-use dispensing rates are limited so 

as to be compatible with the certification procedure. ' If 

the in-use and certification rates are compatible, onboard 

systems would perform as designed. This would also have 

the effect of reducing spillage in-use due to the fuel 

spitback which often accompanies nozzle shut-off. 

The Agency has pursued the development of a voluntary 

in-use dispensing rate standard with the American Petroleum 

Institute (API), which represents petroleum industry 

interests. As summarized in their statement of August 6, 

1986 [17], API has concluded that it is not feasible to 

develop a voluntary standard. API also concluded that it 

should be the motor vehicle manufacturers' responsibility 

to develop refueling control systems which cause nozzle 

shutoff without spitback if design flow limits are exceeded. 

"Spillage" is any loss of gasoline during a refueling 

event due to: dripping from the nozzle spout, 

spitback, or overflow. "Spitback" is the loss of 

gasoline from the fillpipe which sometimes occurs in a 

refueling event when pressure builds up in the fuel 

tank and the automatic shut-off mechanism of the fuel 

nozzle is activated. 

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While recognizing the position taken by API, EPA 

believes that it is more appropriate to limit in-use 

dispensing rates to a level equivalent to that which 

manufacturers must use in certifying the performance of 

their onboard systems. Since the 10 gpm limit has been 

selected to encompass most current industry practice, it 

will impose little or no burden on station owners. On the 

other hand, it will provide manufacturers a fixed target 

for system designs by making maximum certification and 

in-use dispensing rates the same. EPA does not believe it 

is reasonable or practical to require manufacturers to 

certify onboard system performance for undefined, ever 

increasing flow rates. Therefore, EPA has decided to 

propose the limits contained in today's proposal. 

More specifically, the proposed method for controlling 

the in-use dispensing rate is to require that every 

gasoline retailer or wholesale purchaser-consumer (as 

defined in 40 CFR 80.2(k) and (o), respectively) equip each 

pump from which gasoline is introduced into motor vehicles, 

with a nozzle that shall dispense gasoline at a maximum 

flow rate not to exceed 10 gpm. This approach, patterned 

after current nozzle spout diameter regulations for leaded 

and unleaded fuels, places responsibility directly on the 

retailer or wholesale purchaser-consumer [nozzle owner]. 

Enforcement of this alternative would be by direct flow 

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measurements at the station.* Since all aspects of 

compliance would be the owners responsibility, assignment 

of liability for violations would be straightforward, 

although the testing requirement would represent some 

increased enforcement burden for EPA. 

The Agency believes that little or no cost to station 

owners will be associated with this aspect of the 

proposal. Pumps at most stations already meet the 10 gpm 

limit and will therefore be able to retain existing 

nozzles. For those stations which require some reduction 

in flow rate, actual cost for a simple flow limiting 

device, such as a limiting-flow orifice, should be 

minimal. Therefore, the proposed limits do not affect the 

cost of today's proposal given elsewhere in this document. 

EPA is proposing the in-use flow rate restriction 

under Section 211(c) of the CAA. This provision allows EPA 

to regulate or prohibit the offering for sale of any fuel 

if the emission products of such fuel (in this case, the 

refueling vapors or evaporated spilled fuel associated with 

high dispensing rates) will impair, to a significant 

degree, the performance of the emission control device or 

The Agency intends to develop an in-use compliance 

test procedure for measuring dispensing rates in a 

separate action. The test procedure will utilize 

either an in-line flow meter or a volume/time 

measurement technique. 

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system. The flow rate restriction proposed today is 

intended to enhance the performance of refueling control 

systems in actual use, by limiting the in-use rate to the 

certification test flow rate. In addition, even moderate 

amounts of gasoline spillage can offset the emission 

reductions to be achieved through onboard systems and could 

cause the refueling standard to be exceeded. A dispensing 

rate limit will reduce gasoline spillage and help ensure 

the effectiveness of onboard controls. 

Section 211(c) further requires the Administrator to 

consider available scientific and economic data on possible 

alternative emission controls, which would not require such 

a limitation on fuel sales. In this case, the only 

alternative that might be advanced would be to require 

Stage II instead of onboard. That alternative has been 

exhaustively analyzed by EPA, as described earlier in 

today's notice, and has been rejected. Moreover, Stage II 

systems would also likely include flow rate limits of their 

own. Therefore, the Agency believes the proposed in-use 

flow rate restriction is consistent with Section 211(c) . 

EPA requests comment on all aspects of its proposal to 

regulate nozzle flow rates, including such areas as the 

need for control, liability aspects, hardware costs of flow 

regulating controls and alternative regulatory schemes. 

For further information on the effects of in-use dispensing 

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rates and nozzle geometries, an EPA technical report 

entitled "Investigation of the Need for In-Use Dispensing 

Rate Limits and Fuel Nozzle Geometry Standardization" is 

available in the public docket.[18] 

EPA is also seeking comment on the need to standardize 

nozzle geometries. As noted in the discussion of the 

refueling test procedure, EPA has received comment 

indicating that different nozzle spout designs may affect 

onboard efficiency and contribute to refueling spillage. 

If this were the case, EPA would consider it an in-use 

issue as well as a testing issue. That is, if it became 

necessary to standardize test nozzles, then EPA would also 

expect to standardize commercial nozzles. This would be 

absolutely necessary to insure compatibility between 

commercial nozzles and onboard systems designed around the 

certification test procedure. Since all current nozzle 

geometries are relatively similar, however, such 

standardization may not be absolutely necessary. The 

Agency solicits comments from concerned parties on this 

issue. Comments are especially solicited which identify 

the principle parameters of concern and quantify the 

claimed impact of nozzle designs. If significant impacts 

are identified which cannot be accommodated in onboard 

system designs, EPA's preferred course of action would be 

to establish voluntary nozzle design standards through 

combined efforts with professional and trade organizations. 

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However, such standards could also be included in EPA's 

final rulemaking on today's proposal. 

H. Safety Issues Related to Onboard Controls 

Section 202(a)(6) of the CAA directs the Agency to 

consult with the Department of Transportation (DOT) 

concerning motor vehicle safety before requiring the use of 

onboard control technology. During the development of 

today's proposal,. consultations were held with 

representatives of DOT'S National Highway Traffic Safety 

Administration (NHTSA) to discuss the potential safety 

hazards associated with onboard controls. During these 

discussions, EPA's analysis [19] was reviewed and the 

Agency sought NHTSA's review and comment on each of the 

safety issues identified. It is EPA's finding that there 

appears to be no obstacle which would prevent the design 

and production of safe onboard systems, although additional 

study may be necessary before final rulemaking action to 

ensure adequate leadtime is available for vehicle design 

and testing. The Agency, of course, will continue to be 

responsive to the Congressional mandate by consulting 

further with DOT on potential safety concerns as new 

information on probable system designs becomes available. 

A final safety evaluation will be made as part of the final 

rulemaking. 

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The Agency has also met with the Insurance Institute 

for Highway Safety (IIHS). This trade association, which 

is supported by the nation's property and casualty 

insurers, has expressed general concerns to EPA regarding 

the safety of onboard vapor recovery systems in vehicle 

accidents. The views expressed by IIHS have been fully 

considered in EPA's safety analysis and will be included in 

the evaluation supporting the final rulemaking. 

It is EPA's belief that no increase in overall safety 

risk should be accepted because of the presence of onboard 

control systems. Of course, the final choices about exact 

system designs will be with the manufacturers, but EPA 

would not adopt an onboard program unless it were clear 

that safe fuel system designs were available and the 

requisite hardware could be incorporated in the motor 

vehicle fleet within the leadtime provided by the 

regulation. At this time EPA believes that this is the 

case. In fact, the Agency's analysis indicates that it 

would be quite possible for fuel system safety to improve 

along with the adoption of onboard controls. One example 

of how this might occur would be through the use of 

flexible bladders inside the fuel tank to contain the 

liquid fuel and eliminate the presence of any fuel vapors. 

Such containment would improve fuel system safety and also 

eliminate the need for much of the evaporative control 

hardware already on current vehicles (e.g., reduce or 

eliminate the need for the vapor storage canister). 

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There are other aspects of overall fuel system design 

which might be modified at the time of introducing onboard 

controls. Such things as the placement and configuration 

of the fuel tank, the use of side fill versus rear fill 

fueling designs, and external versus internal fueling vapor 

vent lines, are all areas of design determined as a result 

of tradeoffs between competing design goals. EPA believes 

that current fuel system designs can be improved in such 

areas as these and that the safety of onboard equipped 

vehicles need not be compromised. 

Several specific design-related safety issues have 

been raised as being of greatest concern in the design of 

onboard systems. The potential problem areas involve fuel 

spillage, fuel tank pressurization, and vapor storage 

canister location. Each of these areas is discussed 

separately below. 

The concern with fuel spillage centers on preventing 

the escape of liquid gasoline from a vehicle's fuel tank as 

a result of the vehicle rolling over in an accident. The 

high vapor flowrates associated with refueling require the 

use of relatively large diameter vapor line (i.e., 

approximately 1/2 to 3/4 inches in inner diameter) to 

minimize system back pressure as vapors are forced from the 

fuel tank to the carbon canister. Without a rollover 

protection system, such a large vapor line could lead to a 

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substantial fuel spill under certain circumstances, with an 

attendant risk of fire. 

Fuel spills resulting from motor vehicle accidents are 

regulated by DOT in Federal Motor Vehicle Safety Standard 

(FMVSS) 301.* For onboard systems to comply with the 

reguirements of this standard, a rollover valve would have 

to be included in the vent line to automatically close if 

the vehicle rolled over. For various reasons, 

manufacturers would most likely design this valve to remain 

closed in most normal operating modes, and open only during 

the refueling process. Several specific designs have been 

suggested for just such a valve by the developers of 

prototype onboard control systems. Generally, the valve is 

located at the fillneck mouth and is mechanically activated 

by the insertion of the nozzle into the fillneck mouth. 

Although it is unclear which of the valves currently in 

development would be best for ultimate use, the valve is 

conceptually simple and would require no new technology. 

The concern about fuel tank pressurization during the 

refueling operation is related to the use of a mechanical 

fillneck seal to prevent the escape of fuel vapors to the 

atmosphere. This device is installed in the mouth of the 

Federal Motor Vehicle Safety Standard 301 regulates 

the rate at which fuel is allowed to flow from a 

vehicle following a collision and vehicle rollover. 

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fillneck and creates a physical seal between the nozzle 

spout and the fillneck when the nozzle is inserted. Under 

some failure scenarios, if the fuel tank becomes 

overfilled, the resulting excess pressure in the tank could 

cause fuel to squirt out between the nozzle and seal, or 

out of the fillneck when the nozzle was removed. This 

problem can be avoided by including a relief valve in the 

system to ensure that pressure is released from the fuel 

tank before it could reach a dangerous level. Such devices 

are not complex or difficult to design. Furthermore, other 

methods of sealing the fillneck are available (i.e., the 

liquid seal) that completely avoid this potential problem. 

The last potential safety problem concerns the 

location of the onboard canister. If a refueling canister 

were already full, or the system were tampered with so that 

the vent line to the canister was disconnected, refueling 

vapors could be vented into the space near the canister 

when the vehicle was refueled. There is some concern that 

if the canister were located in the engine compartment and 

this situation occurred, a spark, or some other ignition 

source, could cause an explosion or fire. The extent to 

which this could actually become a problem is not 

completely clear at this time. Evaporative emissions 

control canisters, which are similar to onboard canisters, 

are often located in the engine compartment and are not 

known to present a safety hazard. In any case, it appears 

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that this potential problem could be resolved by locating 

the canister outside of the engine compartment, possibly in 

a fender well or near the fuel tank. However, EPA will 

continue to study this safety question, in consultation 

with DOT, to ensure that it is fully resolved before a 

final refueling regulation is issued. 

Overall, the Agency finds that the design experience 

with existing, evaporative emission control systems should 

be useful in designing onboard systems and that there is 

nothing extraordinary about the equipment needed to assure 

safe operation. Furthermore, each of the potential safety 

hazards discussed above is well known to the various motor 

vehicle manufacturers, and can be accommodated in designing 

onboard systems. For these reasons, EPA believes that 

practical and effective onboard systems can be designed and 

built, at a reasonable cost, that will not adversely affect 

vehicle safety. 

Finally, the interaction between safety and leadtime 

should be mentioned. EPA acknowledges the need to provide 

adequate time for development and crash testing in order to 

fully integrate onboard-related hardware into existing 

vehicles. The Agency believes that a minimum of two years 

of leadtime between promulgation of the final rule and its 

effective date will be necessary to complete these and 

other related activities, and fully address safety 

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concerns. However, the Agency acknowledges that some 

uncertainty exists regarding the length of time which may 

be necessary to complete development and crash testing for 

all vehicles. To ensure adequate leadtime is provided in 

the final rulemaking, EPA solicits comments on the leadtime 

issue, with emphasis on specific safety-related areas. 

The Agency is also considering a gradual phase-in of 

refueling controls over a multi-year period in order to 

ease the burden associated with simultaneous emissions and 

safety certification. Such a phase-in could also be 

advantageous if some individual vehicle configurations were 

to require added leadtime to address safety-related issues. 

Regardless of whether all vehicles are ultimately 

reguired to meet an onboard standard beginning in the same 

model year, or a phase-in of controls is allowed, EPA is 

committed to ensuring that manufacturers have adequate 

leadtime to address potential safety concerns. In fact, 

the Agency would be especially open to allowing more 

leadtime if it would result in enhancing overall vehicle 

safety. A more detailed discussion of EPA's leadtime 

analysis is contained in the next section. 

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I. Leadtime 

Section 202(a)(6) of the CAA requires EPA to provide 

adequate leadtime before the implementation of a final 

onboard rule, so that the regulated industry has sufficient 

opportunity to prepare for compliance with the standards 

set forth in the rule. As in the case of other motor 

vehicle emission standards, this involves component and 

system design, vehicle development and proveout, tooling, 

and certification. EPA has carefully considered the impact 

that a refueling emission regulation will have and believes 

that, although some uncertainty exists (especially as 

related to safety), a miniumum of 24 months after 

promulgation will be necessary to provide manufacturers 

with sufficient leadtime to comply with the refueling 

emission standard. The 24 month minimum period allows 12 

months for component/system design and vehicle development 

and proveout. An additional 12 months is provided for 

certification (emissions, fuel economy, and safety). 

Vehicle and component tooling actions can occur 

simultaneously with development or certification. Thus, 

EPA is proposing a minimum two year leadtime for 

manufacturers to implement the onboard standard. 

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The Agency's rationale for the adequacy of a minimum 

two year leadtime is detailed in the response to public 

comments document.[12] In general, EPA's one year 

allowance for onboard system development and design may be 

adequate based on the following considerations. Onboard 

technology is very similar to that used in current 

evaporative emission control systems. With the exception 

of two onboard system components (the fillpipe seal and 

fuel tank valve), all hardware items resemble those, 

presently used in evaporative emission control systems. 

EPA expects onboard systems will utilize activated carbon 

for hydrocarbon storage and air stripping for 

regeneration. While improvements in the air stripping or 

"purge" system probably will be necessary, these 

improvements should involve the extension of existing air 

management techniques and equipment. Even the new 

components needed for onboard systems pose no serious 

development problems because several parties have already 

proposed and demonstrated fillpipe seal and fuel tank valve 

designs. In fact, most manufacturers have already begun 

active onboard system development, and EPA believes all 

system design parameters are well defined with no major 

uncertainties. 

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On the other hand, EPA recognizes there may be some 

uncertainty regarding the adequacy of the 12 month period, 

if developing onboard systems for certain vehicle 

configurations were to take longer than is now expected. 

To address this uncertainty, specific, detailed comments 

are requested on the length of time necessary to complete 

the design and development of onboard systems for all 

vehicles. 

In addition to system design and development, EPA 

believes manufacturers may be able to make any necessary 

component or vehicle tooling changes within the 24 months 

of leadtime. It is not necessary for all pre-production 

compliance preparation actions to occur sequentially; much 

of it can be completed in parallel. In this particular 

rulemaking, the only critical path items that should 

proceed in sequence are component/system design, vehicle 

development/proveout and certification. Any necessary 

tooling changes can be performed in parallel with these 

critical path items. 

Once onboard system vehicle development and proveout 

work is completed, the certification process can begin. 

While 12 months is normally adequate leadtime for 

manufacturers to certify, EPA also recognizes that the 

implementation of refueling controls may present a unique 

situation. Some uncertainty exists in the 12 month 

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estimate because manufacturers will be facing 

recertification of their entire product lines and the 

Federal Test Procedure will be expanded to include a 

refueling emissions test. Manufacturers also need to 

conduct vehicle safety crash testing to assure compliance 

with FMVSS 301. Simultaneous emissions and safety 

certification have occurred previously, but not for all 

three vehicle classes (light-duty vehicles, light-duty 

trucks, and heavy-duty vehicles) in the same model year. 

Comments specifically addressing this aspect of EPA's 

leadtime analysis are invited. 

One way to reduce the certification burden would be to 

use a gradual phase-in approach to refueling controls 

rather than requiring all vehicles to comply in the same 

year. Such an approach could involve the phase-in of 

onboard controls over a two- or three-year period, with the 

majority of vehicles being require to comply in the first 

year (e.g., 70 percent of production certified in the first 

year, 90 percent in the second and the remainder certified 

in the third year). Such a "front-loaded" phase-in period 

would also provide more time to deal with any unique 

onboard system packaging problems, or safety-related 

concerns. In addition, it could actually improve the cost 

efficiency of controls by permitting manufacturers to 

forego development of onboard systems for vehicle models 

scheduled for elimination by the end of the phase-in period. 

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A gradual phase-in might also be an especially 

appropriate means of dealing with onboard controls for 

heavy-duty gasoline vehicles. Historically, heavy-duty 

emission control technology has been based on systems 

developed successfully for light-duty applications. 

Although refueling emission control technology is basically 

identical for either vehicle type, heavy-duty onboard 

control presents some additional concerns because of the 

significantly larger canister capacity requirements and the 

inherent complexity of the two part heavy-duty test 

procedure. A front-loaded onboard phase-in period would 

allow manufacturers to certify most light-duty vehicles and 

trucks in the first year while allowing additional time for 

heavy-duty vehicles and/or any isolated light-duty problem 

cases. As already noted, EPA is open to comment on the 

adequacy of 12 months for certification, but asks that any 

request for additional leadtime or a phase-in period should 

be supported by specific, concrete information 

demonstrating the need for additional leadtime and 

justifying any suggested phase-in period. 

Another way to reduce the certification burden would 

be to allow carryover of exhaust durability data for 

previously-certified LDV family/system combinations for the 

initial year of the new standards. Since LDV engine 

families constitute about two-thirds of all engine families 

subject to certification requirements, providing LDV 

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exhaust emission durability carryover would also represent 

a significant decrease in the initial recertification 

burden associated with the proposed refueling regulations. 

However, one potential problem with this approach concerns 

how well pre-refueling control deterioration data would 

represent emissions from new vehicles with different purge 

systems operating on potentially different certification 

fuel. EPA invites comments regarding how these concerns 

might be addressed and the appropriateness of the use of 

durability data carryover for LDVs to reduce the burden of 

the initial recertification effort. 

Overall, then, EPA believes a leadtime period of at 

least two years may be adequate for the vast majority, if 

not all, vehicle families. All previous evaporative 

emission standards have been implemented with two years of 

leadtime. Due to the importance of ensuring adequate 

leadtime, especially as it relates to addressing any 

potential safety concerns, EPA remains open to comment on 

leadtime and on the need for a phase-in period. 

J. Economic Impact 

The complete economic analysis of this rule is 

contained in the draft Regulatory Impact Analysis (RIA), 

which is available in the docket. The highlights of the 

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analysis are summarized here. All figures are in 1986 

dollars, and a ten percent discount rate is assumed. 

1. Light-Duty Vehicles 

The aggregate cost to the nation resulting from the 

first five years of a refueling emission control 

requirement for light-duty vehicles is estimated to be $602 

million, discounted to 1990. This estimate includes fixed 

costs of $46 million for development and design, $29 

million for recertification, and all necessary hardware 

costs. Because the addition of onboard refueling emission 

control systems is expected to have an impact on vehicle 

fuel consumption, the aggregate cost also includes an 

allowance for the expected net change in operating costs. 

Manufacturers are projected to recover their costs 

through an estimated increase of approximately $17 in the 

purchase price of an average light-duty vehicle produced 

during the first five years. Vehicle owners are projected 

to recover an average of approximately $4 of this cost over 

the life of the vehicle through improved fuel consumption. 

2. Light-Duty Trucks 

The total five year aggregate cost to the nation 

resulting from a refueling emission control requirement for 

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light-duty trucks is estimated to be $266 million, 

discounted to 1990. This estimate includes fixed costs of 

$21 million for development and design, $12 million for 

recertification, and all necessary hardware costs. As with 

light-duty vehicles, the aggregate cost also includes an 

allowance for the expected decrease in operating costs. 

Manufacturers are projected to recover their costs 

through an estimated increase of approximately $23 in the 

purchase price of an average light-duty truck produced 

during the first five years of the standard. Single fuel 

tank light-duty truck prices would increase by $18; dual 

tank truck prices would increase by $42. Truck owners are 

expected to recover an average of approximately $6 of this 

cost over the life of the vehicle due to improved fuel 

consumption. 

3. Heavy-Duty Gasoline Vehicles 

The total five year aggregate cost to the nation for 

heavy-duty gasoline vehicles is estimated to be $25 

million, discounted to 1990. This estimate includes fixed 

costs of $2.5 million for development and design, $3 

million for recertification, and all necessary hardware 

costs, as well as an allowance for the expected net change 

in operating costs. 

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Manufacturers are projected to recover their costs 

through an estimated increase of approximately $31 in the 

price of an average new heavy-duty vehicle produced during 

the first five years of the standard. For smaller 

heavy-duty gasoline vehicles this price increase is 

expected to average $26; for larger ones an average price 

increase of $44 is expected. Vehicle owners are projected 

to recover an average of approximately $15 of this cost 

over the life of the vehicle through improved fuel 

consumption. 

4. Aggregate Impacts 

The total five year aggregate cost to the nation 

resulting from refueling emission control standards for.all 

gasoline fueled vehicles is estimated to be $892 million 

discounted to 1990. This estimate includes fixed costs of 

$70 million for development and design, $44 million for 

recertification, and all necessary hardware costs. The 

aggregate cost also includes an allowance for the expected 

net decrease in operating costs for vehicles produced in 

those five years. 

The average first price increase for all gasoline 

vehicle classes will be approximately $19. Likewise, the 

average fuel recovery credit is expected to be 

approximately $5. 

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The overall socioeconomic impact of these regulations 

is expected to be minimal. Auto and truck manufacturers 

are expected to have no trouble underwriting the capital 

investment required and vehicle sales will not be impacted 

by the very small first price increase caused by onboard 

controls. Employment in the automotive and related 

supplies industries may increase slightly as the result of 

the need to manufacture and install onboard control 

systems. These regulations are not expected to have any 

net effect on the balance of trade. Any increase in the 

manufacturer's invoice price of imported vehicles should be 

offset by the reduction in oil imports permitted by the net 

fuel consumption improvement. 

VII. Public Participation 

Comments and the Public Docket. As in past rulemaking 

actions, EPA desires full public participation in arriving 

at final decisions. In addition to those areas where 

specific comment has been requested earlier in this 

preamble, EPA solicits comments on all aspects of today's 

proposal from all interested parties. Wherever applicable, 

full supporting data and detailed analyses should also be 

submitted to allow EPA to make maximum use of the 

comments. Commenters are especially encouraged to provide 

specific suggestions for changes to any aspects of the 

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proposal that they believe need to be modified or 

improved. All comments should be directed to the EPA 

Central Docket Section, Docket No. A-87-11 (see 

"Addresses"). 

Persons intending to participate in the hearings may 

submitt written questions on any matters relevant to this 

proposal to the presiding officer at any time. To the 

extent that time permits the presiding officer, at his 

discretion, may direct these questions to witnesses 

testifying at the hearing or as appropriate to EPA 

personnel present at the hearing for answers. If time does 

not permit all such written questions to be addressed at 

the hearing, EPA will provide the remaining questions to 

the appropriate witnesses or EPA personnel for written 

response to be placed in the rulemaking docket. 

Public Hearing. Any person desiring to present 

testimony at the public hearing (see "Dates") should notify 

the contact person listed above of such intent at least 

seven days prior to the day of the hearing. The contact 

person should also be provided an estimate of the time 

required for the presentation of the testimony and 

notification of any need for audio/visual equipment. A 

sign-up sheet will be available at the registration table 

the morning of the hearing for scheduling of the order of 

testimony. 

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It is suggested that sufficient copies of the 

statement or material to be presented be brought to the 

hearing for distribution to be audience. In addition, it 

will be helpful for EPA to receive an advance copy of any 

statement or material to be presented at the hearing at 

least one week before the scheduled hearing date, in order 

for EPA staff to have adequate time to give such material 

full consideration. Such advance copies should be 

submitted to the contact person listed above. 

The official record of the hearing will be kept open 

for 30 days following the hearing to allow submission of 

rebuttal and supplementary testimony. All such submittals 

should be directed to -the EPA Central Docket Section, 

Docket No. A-87-11 (see "Addresses"). 

The hearing will be conducted informally, and 

technical rules of evidence will not apply. Written 

transcripts of the hearing will be made. Anyone desiring 

to purchase a copy of the transcript should make individual 

arrangements with the court reporter recording the 

proceedings. 

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VIII. ADMINISTRATIVE DESIGNATION AND REGULATORY ANALYSIS 

The Administrator has determined that this proposal 

constitutes a major proposed regulation, and accordingly a 

Draft Regulatory Impact Analysis has been prepared as 

required under Executive Order 12291. This analysis 

includes detailed assessments of the estimated economic and 

environmental impacts of the regulations proposed here, as 

well as more thorough analyses of the technological 

feasibility of the emission standards and other regulatory 

provisions proposed here, and the alternatives that were 

considered in the development of this proposal. 

The Draft Regulatory Impact Analysis has been placed 

in the public docket referenced at the beginning of today's 

notice. In addition, interested parties may obtain single 

copies through a written request to the public contact 

listed previously. 

This proposed regulation also was submitted to the 

Office of Management and Budget (OMB) for review as 

required by Executive Order 12291. Any written comments 

from OMB and EPA response to those comments have been 

placed in the public docket for this rulemaking. 

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P.97 

IX. IMPACT ON SMALL ENTITIES 

Section 605 of the Regulatory Flexibility Act requires 

that the Administrator certify regulations that do not have 

a significant impact on a substantial number of small 

entities. I certify that this proposed regulation will not 

have such an effect because it primarily affects only 

manufacturers of motor vehicles and motor vehicle engines, 

a group which does not contain a substantial number of 

small entities. In addition, the proposed nozzle flow rate 

limitation applicable to nozzle owners will not have 

significant impact because it would require little, if any, 

investment. 

X. REPORTING AND RECORDKEEPING REQUIREMENTS 

The information collection provisions relating to the 

proposed refueling emissions standard have been submitted 

to the Office of Management and Budget (OMB) under the 

Paperwork Reduction Act, 44 U.S.C. 3501 et seq. An 

Information Collection Request document has been prepared 

by EPA (ICR No. 738) and a copy may be obtained from Bryan 

C. Wood-Thomas, Information Policy Branch; EPA 401 M 

Street, S.W. (PM-223) Washington, D.C. 20460 or by calling 

(202) 475-8791. Comments may be submitted to EPA at the 

above address, but should also be sent to the Office of 

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P.98 

Information and Regulatory Affairs; Office of Management 

and Budget; 726 Jackson Place, N.W.; Washington, D.C. 20503 

marked "Attention: Desk Officer for EPA." The final rule 

will respond to any OMB or public comments on the 

information collection requirements. 

XI. LIST OF SUBJECTS IN 40 CFR PART 86 

Administrative practice and procedures, Air Pollution 

Control, Gasoline, Motor vehicles, Labeling, Motor vehicle 

pollution. Reporting and recordkeeping requirements. 

Authority for the actions proposed in this notice is 

granted EPA by sections 202, 206, 207, 208, 211, and 301 of 

the Clean Air Act [42 U.S.C. 7521, 7525, 7541, 7542, and 

7601] . 

Dated: , 1986. 

Lee M. Thomas, Administrator 

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References 

1. "Recommendation on Feasibility for Onboard 

Refueling Loss Control," U.S. EPA, OANR, OMSAPC, February 

1980. 

2. "Evaluation of Air Pollution Regulatory 

Strategies for Gasoline Marketing Industry," U.S. EPA, OAR, 

OAQPS and OMS, EPA-450/3-84-012a, July 1984. 

3. "Draft Regulatory Impact Analysis—Proposed 

Refueling Emission Regulation for 1990 and Later Model Year 

Gasoline-Fueled Motor Vehicles, Volumes 1 and 2," U.S. EPA, 

OAR, OAQPS and OMS, EPA-450/3-87-001a and b, July 1987. 

4. "Refueling Emissions from Uncontrolled 

Vehicles," Rothman, D. and R. Johnson, U.S. EPA, OAR, OMS, 

ECTD, EPA-AA-SDSB-85-6, 1985. 

5. "Factors Influencing Benzene Emissions From 

Passenger Car Refueling," Laing, P., SAE Paper no. 861559, 

October 1986. 

6. "Air Quality Criteria for Ozone and Other 

Photochemical Oxidants," U.S. EPA, ORD, 

EPA-600/8-84-020aF, August 1986. 

7. "Interim Quantitative Cancer Unit Risk Estimates 

Due to Inhalation of Benzene," EPA-600/X-85-022, February 

15, 1985. 

8. "Study of Gasoline Volatility and Hydrocarbon 

Emissions from Motor Vehicles," U.S. EPA, OAR, OMS, ECTD, 

EPA-AA-SDSB-85-5, November 1985. 

9. "Public Hearing on the EPA Study of Gasoline 

Volatility and Hydrocarbon Emissions from Motor Vehicles," 

Ann Arbor, MI, February 4-5, 1986. (Public Docket No. 

A-85-21, Entry II-F-1.) 

10. "Response to Claim that EPA is Legally Required 

to Impose Stage II Gasoline Controls in all Ozone 

Nonattainment Areas," Ralph Colleli and Richard Ossias, 

U.S. EPA, OGC, to Docket No. A-87-11, June 1987. 

11. "Summary and Analysis of Comments on the 

Recommended Practice for the Measurement of Refueling 

Emissions," U.S. EPA, OAR, OMS, ECTD, March 1987. 

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P.1 

References (cont'd) 

12. "Evaluation of Air Pollution Regulatory 

Strategies for Gasoline Marketing Industry — Response to 

Public Comments," U.S. EPA, OAR, July 1987. 

13. "Evaluation of the Feasibility of Liquid 

Fillneck Seals," U.S. EPA, OAR, OMS, ECTD, 

EPA-AA-SDSB-86-3, December 1986. 

14. "Vehicle Onboard Refueling Control," American 

Petroleum Institute, March 1986, API publication no. 4424. 

15. "Draft Recommended Test Procedure for the 

Measurement of Refueling Emissions," U.S. EPA, OAR, OMS, 

ECTD, EPA-AA-SDSB-85-5a, July 1985. 

16. Memorandum to R. Fred Holbert, U.S. EPA, from W. 

M. Kreucher, Ford Motor Company, June 17, 1986. 

17. "API Response to EPA Request for Comments on 

Petroleum Marketing Industry Refueling Rate Voluntary 

Standard", American Petroleum Institute, August 6, 1986. 

18. "Investigation of the Need for In-Use Dispensing 

Rate Limits and Fuel Nozzle Geometry Standardization," U.S. 

EPA, OAR, OMS, ECTD, EPA-AA-SDS-B-87-07, May 1987. 

19. "Safety Implications of Onboard Refueling Vapor 

Recovery Systems," U.S. EPA, OAR, OMS, ECTD, 

EPA-AA-SDSB-87-05, June 1987. 

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