EPA-420-S-91-100 Docket Number: A-87-11 Document Number: 76) 1V-A Summary of Changed Circumstances Control of Air Pollution From New Motor Vehicles and New Motor Vehicle Engines; Refueling Emission Regulations for Gasoline- Fueled Light-Duty Vehicles and Trucks and Heavy-Duty Vehicles August 1991 Standards Development and Support Branch Emission Control Technology Division Office of Mobile Sources Office of Air and Radiation U.S. Environmental Protection Agency ------- On August 19, 1987 EPA published in the Federal Register a Notice of Proposed Rulemaking (NPRM) for the control of vehicle refueling emissions (52 FR 31162). This document provides a summary of relevant changed circumstances since the NPRM was published. Section I details the changed circumstances and Section II provides a discussion of the impact of these changed circumstances on the proposed action. The changed circumstances discussed in this document arise from three sources. First, the 1990 Clean Air Act Amendments (CAAA) include changes to the provisions related to onboard and Stage II controls. Second, technology developments and several recent/pending regulatory actions have potential effects on EPA's analyses related to onboard controls. Third, comments received following issuance of the NPRM indicate that changes may be appropriate for several aspects of the proposal. I. Changed Circumstances This section discusses the changed circumstances since issuance of the NPRM. The first portion discusses proposed or final regulatory actions and technology improvements. These include fuel volatility control requirements, the requirements for improved evaporative emissions control, and vapor control technology improvements. The second portion addresses changes due specifically to enactment of the 1990 CAAA, including onboard applicability, the level of the emission standard, and implementation leadtime. The third portion discusses test procedure changes which may be appropriate, based on comments received on the NPRM and the proposed changes in evaporative emission test procedures. A. Fuel Volatility Regulation The regulation of gasoline fuel volatility was proposed at the same time as the August 1987 onboard proposal. However, because the specific requirements for volatility control had not been finalized at that time, EPA's onboard analysis assumed that onboard designs would be based on a fuel volatility of 11.5 psi Reid vapor pressure (RVP). EPA has since promulgated a final rule requiring that, beginning in 1992, fuel volatility be limited to a maximum of 9.0 psi RVP in the summer months, when control of ozone-producing emissions (including refueling vapors) is most critical (55 FR 23658, June 11, 1990). Fuel volatility of 7.8 psi RVP is called for in some southern nonattainment areas. The volatility specification for certification test fuel will remain at 9.0 psi RVP, thus ensuring that in-use fuel volatility will not exceed design basis fuel volatility in the critical control months. These controls affect several areas of the analysis which accompanied the onboard control proposal. The most significant ------- effect is a decrease in the amount of refueling emissions generated. Although there is some variation among vehicles, there will typically be a decrease of about 11 percent in the amount of emissions to be controlled, thus reducing the air quality benefit of refueling controls somewhat. However, for onboard systems, this also allows a reduction in canister size from that estimated in the NPRM analysis. Purge requirements will also be eased somewhat. Because smaller canisters are less expensive and easier to package, it would be reasonable to expect that overall costs would be lower. B. Improved Evaporative Emissions Control Section 202 (k) of the amended Clean Air Act requires EPA to promulgate regulations to improve the control of evaporative emissions from gasoline-fueled motor vehicles. These regulations must ensure emissions control during vehicle operation and over at least 2 days of nonuse. Even before the CAAA were finalized, EPA had proposed changes to the evaporative test procedure as part of the original proposal to control in-use fuel volatility (52 FR 31274, August 19, 1987). This was supplemented by an additional notice on January 19, 1990 (55 FR 1914). A public workshop was held on December 19, 1990 (55 FR 49914, December 3, 1990). The Agency plans to finalize the improved evaporative rulemaking this year. Although improved evaporative system designs will ultimately depend on the test procedure requirements and the control strategies elected by the manufacturers, it is expected that canister sizes would need to be increased to handle increased vapor loads, and that the purge system would need to be upgraded to transport greater amounts of vapor to the engine. Manufacturers would also need to ensure that these greater amounts of vapor do not increase exhaust emissions above the standards. C. Technology Improvements The technology analysis provided in the proposal projected that most onboard control systems would be integrated with the evaporative emissions control system, so that the implementation of onboard controls was considered incremental to current evaporative emissions control requirements. Onboard system concept development and prototype testing since the proposal was issued have indicated that even further design simplifications are possible. Basic components of a simplified design are presented in an EPA memorandum, dated December 22, 1988 (available in Public Docket No. A-89-18, item II-B-6), and in a number of other technical and briefing documents in Public Docket No. A-87-11. As is discussed in these technical documents and briefings, EPA has developed and tested a simplified onboard system in a bench configuration and has installed a version of this system in a late model passenger car. The prototype system met EPA's ------- proposed refueling emission standard and performed satisfactorily in limited in-use testing. D. Applicability of the Standard 1. Vehicle Classes Regulated The August, 1987 proposal covers gasoline-fueled light-duty vehicles (LDVs), light-duty trucks (LDTs), and heavy-duty vehicles (HDVs). The Clean Air Act, Section 202(a)(6), as amended in 1990, directs EPA to "promulgate standards under this section requiring that new light-duty vehicles manufactured beginning in the fourth model year after the model year in which the standards are promulgated and thereafter shall be equipped with [onboard] systems." Light-duty vehicles are explicitly included, but no specific language dealing with other vehicle classes is provided. Section 223 of the amendments defines light-duty vehicles as having the Code of Federal Regulations definition in effect at the time of enactment of the amendments (see 40 CFR 86.082-2). The report of the joint House/Senate conference on the 1990 CAAA contains no legislative history specifically dealing with onboard controls, although it does point out that Title II provisions (which include the paragraph requiring onboard controls) are generally based on the House bill, H.R. 3030 (House Report No. 101-952, 101st Congress, 2nd Session, 336). The report of the House Committee on Energy and Commerce on H.R. 3030, dated May 17, 1990 (House Report No. 101-490, 101st Congress, 2nd Session, 303), contains wording similar to that of the final 1990 CAAA on onboard controls, applying the requirement to "new light-duty motor vehicles". The report goes on to say that "the standards required to be promulgated under this paragraph are to apply to all new passenger cars and all light-duty trucks," implying that the term "light-duty motor vehicles" was intended to include LDVs and LDTs. The Chafee-Baucus Statement of Senate Managers is described by its authors as "our best effort to provide the agency and the courts with the guidance that they will need in the course of implementing and interpreting this complex act" (136 Congressional Record, S16933, daily ed., October 27, 1990). In it they describe the Conference agreement to essentially adopt the House provision for onboard controls, specifically characterizing the House provision as applying "to all new passenger vehicles and light-duty trucks." The legislative history discussed above suggests that Congress may have intended that LDTs be included within the scope of the onboard requirements. In addition, Congress did not preclude imposition of onboard controls based on other statutory authorities. Thus, onboard controls could be required for LDTs and HDVs based on the Clean Air Act's general authority provision, Section 202(a)(1), which states: "The Administrator shall by ------- regulation prescribe (and from time to time revise) in accordance with the provisions of this section, standards applicable to the emission of any air pollution from any class or classes of new motor vehicles or new motor vehicle engines, which in his judgment cause or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare." It is estimated that LDTs contribute about one-third of current total refueling emissions. Exempting LDTs from onboard control requirements would reduce the benefit of the program correspondingly, mitigated perhaps temporarily by the presence of Stage II controls in some non-attainment areas. Furthermore, because many of these vehicles are very similar to LDVs in terms of design, hardware, and usage, controls would be similar. This is reflected in the fact that these vehicle classes are treated together in other provisions of the 1990 CAAA. The incremental cost of onboard controls per light-duty truck is estimated in the EPA memorandum on cost (referenced in Section I.C of this document) to be slightly higher than that of a typical LDV. This is more than offset, however, by fuel recovery credits. The refueling emissions contributed by HDVs are estimated to be about 5 percent of the total. Although much smaller than that of LDVs and LDTs, this is still a significant contribution when viewed in the context of the very high efficiency achievable by, and required for, onboard controls. In addition, many of the smaller HDV designs, such as class lib and III trucks, are essentially extrapolations of conventional LDTs and could use similar control technology. Furthermore, fuel system designs for other gasoline-fueled HDVs are similar to those of lighter vehicles, and so the approaches taken to designing LDV and LDT onboard systems could apply to these larger vehicles as well. 2. Fuel Type Considerations The growing interest in the use of alternative fuels necessitates clarification of which vehicle fuel types are meant to be subject to onboard refueling vapor control requirements. The language in the 1990 CAAA is not specific regarding fuel type and so does not directly resolve this issue. Although the 1987 proposal applied only to gasoline-fueled vehicles, it may be appropriate to broaden any onboard requirement to other fuel types. This would be consistent with EPA's past approach of establishing a level playing field for all fuel types. If such an approach were taken, any vehicles which use a fuel of low enough volatility that they can meet the refueling emissions performance standard without onboard control systems would, of course, not be required to install such systems. In some cases, it may be feasible to waive testing requirements if refueling emissions are inherently low. Vehicles designed to operate on more than one fuel type would need to meet the refueling emissions ------- standard under the fuel composition conditions with the greatest refueling emissions. E. Emission Standard The statutory changes also raise the issue of the appropriateness of the 0.10 gram per gallon (g/gal) emission standard originally proposed in the 1987 NPRM. The 1990 CAAA require a minimum emission capture efficiency of 95 percent. As is shown below, the proposed standard appears to satisfy that requirement. Using the refueling emission rate equation developed by EPA and the limiting values of the applicable parameters specified in EPA's refueling test procedure, the efficiency of the proposed standard is shown below: ER = 0.485 RVP + 0.884 TD - 0.0949 AT - 5.909 = 0.485 (9.0) + 0.884 (81) - 0.0949 (+2) - 5.909 =5.43 g/gal where: ER = the refueling emission rate in g/gal. RVP = Reid Vapor Pressure in psi. TD = Dispensed fuel Temperature in °F. AT = (Tank Temperature - Dispensed fuel Temperature) in °F. The efficiency is therefore calculated to be: 1 - (0.10 * 5.43) = 0.98 or 98%. In the August 1987 NPRM, certification useful life, recall testing, and warranty periods were proposed to be the same for onboard refueling controls as for other elements of the vehicle emission control system (52 FR 31220, August 19, 1987). The amendments to the Act require that, with respect only to LDVs and LDTs up to 3,750 Ibs. loaded vehicle weight and 6,000 Ibs. gross vehicle weight rating, "in the case of any requirement of [Section 202] which first becomes applicable after enactment... the [useful life] period shall be ten years or 100,000 miles (or the equivalent), whichever first occurs, with testing for purposes of in-use compliance under section 207 up to (but not beyond) seven years or 75,000 miles (or the equivalent), whichever first occurs," unless otherwise specified (Section 202(d) (1) ) . With respect to all other vehicles and engines, the periods are presumed to be the same as above unless the Administrator finds that longer periods are appropriate. Warranty periods were shortened by the 1990 amendments to two years/24,000 miles (or the equivalent) for most emission control components including onboard refueling systems (Section 207(i)). One possible approach to implementing these provisions would be to make only the changes to this rule required to make it conform to the CAAA. Taking this approach would mean ------- that, for heavier LDTs and HDVs, the requirements which existed during the time of the NPRM would apply. F. Implementation Leadtime In its 1987 NPRM, EPA estimated, based on its past experience with evaporative emission controls, that a minimum leadtime period of two years would be required to design, develop, and adequately test onboard refueling systems. EPA acknowledged that some uncertainty existed in its estimate and discussed the possibility of using a phase-in approach to reduce the certification burden and provide manufacturers more time to address any model-specific safety concerns. Responding to EPA's proposal, most manufacturers indicated that a minimum of four years leadtime was necessary to ensure safe implementation of onboard controls. Longer leadtime was also recommended by the National Highway Traffic Safety Administration (NHTSA), which stated that it is critical for manufacturers to receive sufficient leadtime in order to minimize safety risks. Congress addressed leadtime for light-duty vehicles, mandating an implementation schedule in the 1990 CAAA. The Amendments require a three year phase-in (40,80,100 percent, applicable to each manufacturer's sales volume) of onboard refueling controls on new light-duty vehicles beginning in "the fourth model year after the model year in which the standards are promulgated." Because it is probable that most vehicle models would be in 1992 model year production before the final rule is promulgated, an onboard phase- in requirement could not become effective before the 1996 model year. G. Refueling Test Procedure It is desirable that the onboard system test procedure provide an accurate assessment of the control of refueling emissions while minimizing the testing burden on both industry and government. The ideas discussed below for modifying the proposed test procedure are based on comments received on the NPRM and anticipated changes in the evaporative test procedure. These alternative approaches, each of which is discussed in further detail below, are as follows: 1) vehicles which have the onboard system integrated with evaporative control systems would use all or part of the Federal Test Procedure1 (FTP) as the preconditioning cycle before a refueling test; 2) abbreviated preconditioning options would be added for non-integrated systems; 3) an abbreviated procedure for testing seals and connections would be added; 4) a four gallon per minute lower limit would be specified for the refueling dispensing rate. 1 The Federal Test Procedure (FTP) refers to the testing sequence that includes the exhaust and evaporative emission systems test procedures. ------- 1. Preconditioning Fully-Integrated and Partially-Integrated Systems The refueling test procedure proposed in the August 1987 NPRM for fully-integrated and partially-integrated systems is a separate, stand-alone sequence which would be performed independently from the FTP sequence. It consists of a vehicle preconditioning sequence followed by the actual refueling emissions measurement test. A diagram of this proposed refueling test procedure is provided in Figure 1. A number of comments on the original onboard refueling control proposal concerned the complexity of the test procedure. Although the proposed procedure was itself the product of interaction between EPA and manufacturers, it still appeared to represent a significant increase in impact on testing resources. These resource impacts were largely associated with the vehicle preconditioning sequence, which involved loading the vapor storage canister to at least the breakthrough point and then simulating three days of normal vehicle driving. Commenters suggested that EPA should develop a simplified approach to refueling testing in order to reduce the test's resource impacts. In response to the comments, the Agency undertook further study aimed at identifying alternative methods for vehicle preconditioning which would be less resource intensive. One concept is to use the FTP for conditioning of integrated refueling/evaporative emission control systems. Since, in the future, the FTP will likely include initial canister breakthrough loading and a combination of vehicle driving and canister loading conditions, the test vehicle and fuel vapor emission control system would be conditioned as they proceed through the FTP to the refueling measurement test. Such an approach could eliminate the need for a special vehicle preconditioning cycle altogether, thus greatly simplifying the overall test procedure, except perhaps in tests run solely for the purpose of assessing compliance with the refueling emission standard. This assessment is based on the FTP sequence proposed in the evaporative emissions workshop notice (55 FR 49914, December 3, 1990); the workshop was held on December 19, 1990. Although currently a proposal, it represents the best projection of the FTP likely to be in use at the time the onboard system test procedure is finalized. A diagram of the FTP proposed in the workshop is shown in Figure 2. It may be necessary to modify this alternative if the proposed FTP is substantially changed in the improved evaporative emissions control rulemaking now underway. ------- r Integrated System T" egg a. Disconnect Vapor Line to Canister b. Drain fuel Tank c. 40?. Fuel ing d. Reconnect Vapor Line to Canister e. Drive One LA 4 f. One Hour Hot Soak g. Repeat (e) and (C) Twice h. Disconnect Vapor Line to Canister i. Drain Fuel Tank j. 40% Fueling k. Reconnect Vapor Line to Canister 1. Heat Uuild (60° 4 2°F Initial, 24 + 1°F Rise) m. Repeat (e) Through (1) Twice n. Drive One LA-4 Can Iste r_Load ing to Breakthrough 0 Drain Fuel Tank 0 Soak Vehicle for 6 Hours 0 Fuel in SHED to Breakthrough Integrated System ig r Purge, Coi»tinugus Dr^ve a. Disconnect Vapor Line to Canister b. Drain Fuel Tank c. 403; Fueling d. Reconnect Vapor Line to Canister e. Drive Repeated LA-4a Until Mileage Accumulated = Mileage Required for Purge Equivalent to Cyclic Drive. Mileage Accumulation Stops at the First Idle Paat the Mileage Requirement Non-integrated System Canister Purge, Continuous Drive a. Disconnect Vapor Line to Canister b. Drain Fuel Tank c. 95% Fueling d. Reconnect Vapor Line to Canister e. Drive Repeated LA-43 Until 85% of Tank Volume Is Consumed Vehicle Cool Down 0 Disconnect Line to Canister 0 Drain Fuel Tank 0 10* Fueling 0 Soak Vehicle 6 to 24 Hours I Refuel ing Emissions Measurement Reconnect Vapor Line to Canister Fuel to Automatic Nozzle Shut-off (B5* Mimimun Fueling). Restart Fueling Following Any Premature Shut-offs Within 15 Secondn) NPRM Onboard Test Procedure Flow Chart Figure 1 ------- Proposed Federal Test Procedure Fuel 9 RVP, 40% full I Preconditioning LA-4 Purge & Load Canister SHED or bench procedure I Refuel Cold Soak 68-86° F Exhaust Test Fuel Temp Profile Refuel Refueling Emissions Measurement Test Two Heat Builds 2 hrs ea, fuel 72-96F natural cool to 72° F Diurnal Test 2 hours fuel 72-96° F Refuel Running Loss Test LA-4,2*NYCC,LA-4, 95F SHED or point source Hot Soak and Permeation Loss Test 5 hours ambient 95° F Refueling Emissions Measurement Test Figure 2 ------- Refueling Test Procedure: Integrated Systems FTP* Through the Exhaust Test Disconnect Refueling Canister Remove Fuel Filler Cap Drain Fuel Tank 10% Fueling Replace Fuel Filler Cap Vehicle Temperature Stabilization (80 ± 3°F for at least 6 hours) Connect Refueling Canister Remove Fuel Filler Cap Place Vehicle in Shed Refueling Emissions Measurement Test Fuel to Automatic Nozzle Shut-off (85% Minimum Fueling : 81° - 84° F Fuel) Restart Fueling Following Any Premature Shut-offs Within 15 Seconds * The Federal Test Procedure (FTP) refers to the testing sequence that includes exhaust and evaporative emission system test procedures Figure 3 ------- For integrated systems, it may be appropriate for the test procedure to adopt one of two options which would use the FTP to condition the vehicle/canister for the refueling emissions measurement test. The first option is shown in Figures 2 and 3 as the sequence labeled option "1". Under this option, the refueling emissions measurement test would be placed at the end of the FTP and would be retained in the same form as that described in the NPRM. The basic premise for positioning the refueling test in this way is that the vapor loads and purge requirements involved in the evaporative emissions test are expected to be generally sufficient to test the integrated system's purge capability and to prepare the system for a refueling event. Therefore, a separate refueling preconditioning would not be needed. One possible issue concerning use of the FTP to condition vehicles/canisters prior to the refueling test is the amount of work that must be performed if the only objective is conducting the refueling measurement test, such as might occur for recall evaluation testing or if the refueling test were voided during certification testing by, for example, the accidental spillage of fuel during refueling. In such instances the entire FTP sequence would have to be performed for the purpose of conditioning a vehicle for a refueling test under Option 1. It may be useful to consider alternative methods of determining if the vehicle conditioning sequence can be further abbreviated, while maintaining proper evaluation of the refueling emission control system. Another possible option is the placement of the refueling emissions measurement test after the exhaust emissions measurement test in the FTP. Labeled option "2" in Figures 2 and 3, this testing option would provide a shorter preconditioning method for integrated systems, and thus would provide a savings in time and resources for those cases in which the only desired objective is the refueling emissions measurement. In this approach, the vehicle/canister would be preconditioned as in the proposed evaporative procedure and the vehicle would be driven through the driving cycles specified in the exhaust test (exhaust measurements may or may not be required). The refueling emissions measurement test would then be conducted. To conduct the evaporative emissions tests under Option 2, the entire FTP would need be performed separately. Alternatively, it is possible to design a test procedure that allows re-entry into the FTP sequence after completion of the refueling emissions measurement test in order to complete the evaporative and running loss portions of the test. Use of this approach would require that additional purge be provided before continuing through the rest of the FTP, because the refueling event would be expected to load the canister to near its full capacity. Additional purge opportunity could be provided by inserting another exhaust emissions driving 11 ------- cycle (without measurement), or some comparable driving sequence, into the FTP after the refueling emissions test. Another approach is to use Option 1 for normal certification testing, but to retain Option 2 as a stand-alone, short test to be used at the Administrator's discretion. This option would provide maximum flexibility and reduce overall testing resource impacts for both certification and in-use compliance testing. 2. Preconditioning Non-Integrated Systems The second test procedure modification which may be appropriate is, again, inspired by the desire to make the onboard system test less resource-intensive. Under the August 1987 onboard proposal, 85 percent of the fuel tank capacity must be consumed during the preconditioning sequence for non-integrated systems. In the modification being considered, the manufacturers would have the option of using any integer number of continuously driven LA-4 driving cycles to sufficiently condition the canister (by the manufacturer's definition) prior to the refueling test (Figure 4), provided that 85 percent or less of the fuel tank capacity is consumed. This modification would be expected to decrease the amount of testing resources required without lessening the test procedure's ability to evaluate the capacity to control refueling emissions. The use of this preconditioning sequence would be expected to lead to similar canister size and purge requirements as the full drivedown (85 percent) option because the manufacturers would still be required to pass the refueling emission test. Consequently, this revised test sequence might be desirable because it provides the opportunity to reduce resource impacts for both the manufacturers and EPA. It should be noted that the option given in the original proposal to use test track/road purge in lieu of vehicle dynamometer driving would be retained. As a possible alternative method for EPA testing of non- integrated systems, a vehicle would be fueled to automatic nozzle shut-off, driven some integer number of LA-4 driving cycles, and then subjected to the refueling emissions measurement test (Figure 4). This method differs from the above-described modification in that the SHED refueling event would directly follow the driving, with no intervening drain and fill to 10 percent, and in that it would be conducted at EPA's discretion only. The basis for this approach is the fact that partial refuelings are common in use and so an onboard system should have adequate design margin to accommodate partial refuelings. The number of LA-4s driven would be at EPA's discretion on a per test basis. 12 ------- Refueling Test Procedure: Non-Integrated Systems Canister Loading Drain Fuel Tank Soak Vehicle for at Least 6 Hours at 80° ± 3° F Load Canister(s) to Breakthrough (Identical to Evap Loading Technique) Continuous Drive Canister Purge Disconnect Vapor Line to Canister Drain Fuel Tank 95% Fueling: 81° - 84° F Fuel Reconnect Vapor Line to Canister Drive the Number of LA-4s Specified by Manufacturers (up to 85% of Fuel Tank) Disconnect Vapor Line to Canister Drain Fuel Tank 10% Fueling Soak Vehicle for at Least 6 Hours at 80° ± 3° F Reconnect Vapor Line to Canister Remove Fuel Filler Cap Place Vehicle in Shed Refueling Emissions Measurement Test > Fuel to Automatic Nozzle Shut-off (85% Minimum Fueling : 81° - 84° F Fuel) Restart Fueling Following Any Premature Shut-offs Within 15 Seconds Testing Option for EPA Disconnect Vapor Line to Canister Fuel to Automatic Nozzle Shut-off (at Least 95% of Fuel Tank, 81-84 F Fuel) Reconnect Vapor Line to Canister Drive Integer Number of LA-4s Determined by EPA Remove Fuel Filler Cap Place Vehicle in Shed Refueling Emissions Measurement Test Fuel to Automatic Nozzle Shut-off (at least as much fuel as used during drive, 81 °-84° F Fuel) Restart Fueling Following Any Premature Shut-offs Within 15 Seconds Figure 4 ------- P.16 The refueling emissions measurement test contains a provision for fueling to automatic shut-off, and, because automatic shutoff is commonly practiced in use (even for small partial fills such as with rental car returns), it would appear reasonable to retain this provision for this test as well. However, the automatic shutoff mechanisms on fuel pumps are not designed to ensure that a measured volume of fuel is in the vehicle fuel tank at shutoff. Therefore, it is likely that the refueling measurement test would add somewhat more or less fuel than was burned during the LA-4 driving cycles, thus introducing uncertainty into the results. The effect of this variability in nozzle shutoff on a test involving just a few LA-4 cycles of drivedown could be significant. Concern about pumping too much fuel would tend to be mitigated by the fact that the rate of hydrocarbon reduction during purge is generally much higher when the canister is heavily loaded with hydrocarbons (i.e. during the initial LA-4 cycles) than when the hydrocarbon concentration in the canister has been reduced, thus helping to ensure that the purge provided by initial drivedown of a fully loaded canister will free up more than enough storage capacity to accommodate the corresponding partial refueling vapor load. EPA would welcome input from others on whether or not the higher purge rates present at the start of a purge cycle would adequately cover for nozzle shutoff uncertainties. To avoid inaccurate test results caused by the pumping of too little fuel, the test procedure would need to ensure that the amount of fuel dispensed during the refueling measurement test is at least as much as that burned during the LA-4 driving. To verify this, some method of determining the amount of fuel consumed during the driving sequence would need to be included, such as by measuring exhaust emissions during some portion of the driving and performing a carbon balance calculation, or by using the vehicle's previously determined fuel economy rating. The amount of fuel pumped during the refueling test would also need to be metered to ensure that, if automatic pump shut-off were to occur before the proper amount of fuel was displaced, refueling would be resumed until sufficient fuel was pumped. EPA would welcome other suggestions for dealing for pump shutoff variability. One of the more attractive features of a non-integrated system (fully separate refueling and evaporative systems) is that it permits a lower purge rate than for an integrated system since the purge of the refueling canister can be spread more evenly over the driving associated with the fuel dispensed. This lower purge rate is valuable since it allows for a reduction in the potential effects of purge on exhaust emissions. Considering the sophisticated purge strategies available with electronic controls, there is some concern that, because of potential purge/exhaust emission interactions, manufacturers could design a purge system which operates at lower purge rates during the exhaust emission test than during a subsequent portion of the preconditioning 14 ------- P.17 driving cycle. To avoid the possibility of adverse or unrepresentative exhaust emission effects, it may be necessary to include a requirement that, for vehicles using non-integrated systems, the purge volume must be essentially the same for each LA- 4 driving cycle during the test. Finally, it may be appropriate to apply the procedure for loading canisters to breakthrough proposed in the evaporative emissions revisions to the FTP (55 FR 49914, January 19, 1990) to tests of non-integrated systems as well as integrated systems. This would simplify testing procedures and reduce the need for additional equipment. Any subsequent changes to the loading procedure resulting from finalization of the improved evaporative rule would be factored in as well. 3. Testing of Seals and Connections Vapor emissions from a refueling emissions test can occur from two sources: emissions vented from the canister and emissions that escape from the fillpipe seal, vapor line connections, and other leaks. The test procedures proposed in the NPRM and the options described above test for both of these sources of emissions. Although the purge/canister system capacity and operation would be evaluated through the full preconditioning and refueling emissions measurement sequence, there may be situations in which it is desirable to only measure emissions arising from areas other than the canister. Therefore, it may be appropriate to add a test procedure option, to be used at EPA's discretion only, in which the canister would be thoroughly bench purged prior to conducting a refueling emissions measurement test. The canister would then be reconnected and the normal refueling emissions measurement test conducted. The emissions would need to meet the refueling emission standard in order to pass the test. The advantage of this type of test over a complete test sequence is that the integrity of the seals and connections can be determined with a modicum of effort in cases where this determination is the only desired result. 4. Lower Limit on Refueling Dispensing Rate In its proposal, EPA had specified a fuel dispensing rate of approximately 10 gallons per minute (gal/min) for refueling tests. An option was included, however, for EPA to test at lower flow rates if desired. This was done to ensure that the Agency would have the ability to adequately test systems which it believed might lose control effectiveness at low flow rates. Based upon comments received, it may be appropriate to specify a lower limit for such testing. Since extremely low dispensing rates would not be expected to occur in use, they would be unrepresentative. Consequently, replacing the 10 gal/min proposed rate with a dispensing rate range of 4-10 gal/min may be a reasonable solution. 15 ------- P.18 Nearly all in-use refuelings occur at a rate of 5 gal/min or greater, and at least some fuel dispensing nozzles themselves fail to operate properly if used at 3 gal/min. II. Impact of Changed Circumstances on the Proposed Action In addition to the impacts on the test procedure discussed in Section I.G, the changed circumstances discussed in Section I of this document have potential impacts on costs, benefits (emissions reductions), and the resulting cost effectiveness of onboard controls. A revised cost analysis, addressing most of the changed circumstances discussed in Section I of this document, is contained in an EPA memorandum, dated December 22, 1988, available in Public Docket No. A-89-18, item II-B-6. This analysis calculated onboard control costs based on a design incremental to improved evaporative controls, a simplified onboard system design concept, and 9.0 psi RVP certification fuel. The resulting estimated cost increment was lower than the NPRM estimate. An adjustment for the fuel recovery credit provided by combustion of the collected vapors resulted in a net average cost savings of a few dollars per vehicle. Since there are Stage II vapor recovery systems in some areas of the country now, and their use is expected to expand to a number of other areas under the CAAA of 1990, it is worthwhile assessing the affects of Stage II on EPA's cost analysis for an onboard equipped vehicle. Based on current onboard and Stage II technologies, refueling events in nonattainment areas in which both onboard and Stage II systems are operative will result in the refueling vapors being captured by the onboard system; thus the onboard fuel recovery credit would be retained. Without this adjustment for the fuel recovery credit it is expected that, instead of a small per vehicle net cost savings, a positive average cost of a few dollars per vehicle would result. The changed circumstances discussed in Section I of this document will produce a small net decrease in emissions reduction benefits of onboard controls, compared to the benefits calculated in the NPRM. The effect of volatility controls was accounted for in the sensitivity analysis in Section V of the NPRM, yielding the conclusion that the annual average gasoline refueling emission factor is about 11 percent less for the case in which summertime RVP is controlled in class C areas at 9.0 psi than the case in which it is set at 11.5 psi. It is also possible that use of reformulated gasoline in some nonattainment areas would cause a slight reduction in benefits. The implementation schedule for onboard controls would obviously impact how quickly emissions reductions would begin to occur. However, it is reasonable to expect that the full annual benefit would eventually be attained as phase-in and fleet turnover progresses. The installation of Stage II systems, required in some 16 ------- P.19 nonattainment areas by the 1990 CAAA, would also temporarily reduce the emissions control benefit of onboard systems. However, because the Act also calls for the retirement of the federally-mandated Stage II control requirements once onboard controls are in widespread use, the reduction in onboard control benefits would be expected to be temporary. It should be noted that the onboard control standards and their implementation schedule are intended to apply to vehicles sold in all parts of the United States, even where Stage II controls are (or will be) in place, such as in California. Because, as discussed above, the net cost of onboard refueling emissions control is projected to be modest, the impact of changed circumstances on calculated benefits does not alter the NPRM's general conclusion regarding cost-effectiveness. 17 ------- |