Stage II Vapor Recovery Pilot Testing Project

April 26, 2000

Prepared By:

Vermont Agency of Natural Resources

Department of Environmental Conservation

Air Pollution Control Division

Acknowledgment: The Air Pollution Control Division (APCD) would like to acknowledge the work conducted by Christopher Penney of Tank Testing Services of New England, Ltd. who performed the testing of the Stage II systems for this project under contract to the APCD. We would also like to extend our thanks and appreciation to all of the station owners who cooperated by allowing this testing at their stations. Through cooperatives like this, the APCD can collect information vital to implementing sound, effective and reasonable rules that protect public health and the environment.

I. Background

In August, 1996, Vermont adopted a regulation requiring Stage II vapor recovery systems on all gasoline dispensing facilities that pump more than 400,000 gallons of gasoline per year. These systems will be phased in over a four year period based on annual throughput as follows:

•by December 31, 1997 if pumping 1,200,000 gallons/year or greater;

•by December 31, 1998 if pumping 1,000,000 gallons/year or greater;

•by December 31, 1999 if pumping 700,000 gallons/year, or greater;

•by December 31, 2000 if pumping 400,000 gallons/year, or greater.

Additionally, the regulation requires all systems to have received California Air Resources Board (CARB) approval. The CARB has a long standing certification program for Stage II systems. In order to achieve certification by the CARB, a Stage II system has to demonstrate compliance with a broad range of criteria including the ability to achieve at least 95% control of refueling emissions. Part of the certification process is for any candidate system to be installed at a gas station and successfully complete a 90 day trial operation in actual use. Other states with Stage II requirements, rely on the CARB certification process to define what are acceptable systems. In addition to the requirement that a Stage II system be CARB certified, Vermont's Stage II regulation requires all Stage II systems to pass functional tests upon installation to demonstrate compliance with performance standards. This testing is done to ensure that the equipment is functioning properly and has been properly installed. Routine retesting to document continued compliance with performance standards is currently required every five years under the regulation. The CARB certifications for most vacuum-assist systems require retesting on an annual basis, and a number of other northeastern states require retesting more frequently than every five years.

Testing conducted at gasoline stations in California by the CARB has indicated that many facilities were not maintaining compliance with performance standards for as long as five years without interim maintenance and repairs. Because the Vermont regulation is not consistent with the CARB or some of the other northeastern states, the Vermont APCD is interested in determining an appropriate approach for maintaining the efficiency of Stage II systems in Vermont. To gain a better understanding of how well existing Stage II systems are maintaining compliance with performance standards, the APCD hired a testing contractor, through a competitive bidding process, to conduct testing of Stage II systems at stations where the systems have been in operation for at least one year. In addition to collecting data on the ability of systems in use to maintain compliance with performance standards, information was also obtained on the level of effort required to bring stations failing tests back into compliance with performance standards. The data collected from this testing will be used to help determine appropriate measures to maintain the efficiency of Stage II systems at stations in Vermont.

II. Methodology

The actual field testing for this project was conducted by Christopher Penney of Tank Testing Services of New England, Ltd. under the direction of the APCD. The stations to be tested were selected by the APCD and had all previously passed the required tests. A total of 35 stations owned by 13 entities, were initially selected and letters were sent to each owner informing them that the APCD wished to retest their stations and explaining the reasons for the pilot testing project (see Appendix 1 for sample letter). Participation in the test project was voluntary and no enforcement actions were initiated based on failed test results. Of the owners of the stations initially selected, three indicated they did not wish to participate. The total of seven stations owned by these three owners were dropped from the testing program. One other station was dropped due to the fact that it had been retested just prior to the initiation of the pilot testing project because of a change in the type of Stage II system. The stations originally chosen were weighted heavily toward bootless vacuum-assist Stage II systems with only one station equipped with a balance system. One of the 11 owners participating in the program agreed to allow testing at five more of its stations, all of which were equipped with balance systems. This allowed testing of nearly the number of stations originally selected (32 vs. 35).

Tests conducted for this project included the pressure decay test at all stations, the air to liquid (A/L) ratio test at all stations equipped with bootless vacuum-assist systems and the vacuum line integrity test at two stations using the Healy Systems, Inc. system with a central vacuum pump. Testing was performed in accordance with the CARB test procedures as modified by the APCD. All pressure decay tests were performed in an "as - is" condition; that is, without first doing any maintenance to facilitate passing the test such as tightening loose tank top fittings or replacing any worn or broken parts. Because this testing was designed to gather data on compliance with performance standards, a special form (Appendix 2) was developed to facilitate recording the causes for non-compliance. The initial pressure decay test was run for the full five minutes and the final result recorded. If the test failed, the technician attempted to identify causes for the failure and any parts identified as contributing to a test failure were recorded on the form. In addition to documenting the causes of a test failure, the technician attempted to bring the system into compliance by tightening leaking fittings and replacing common parts that were leaking such as Stage I poppet valves and fill caps. These relatively minor system components were paid for by the APCD.

For the majority of the stations tested, it had been at least 12 months since they were last tested. One owner, with three stations included in this project, conducts annual Stage II testing as a matter of course. Therefore, these three stations had all been tested approximately four months before they were tested as part of this project. Overall, the time elapsed since the most recent test at the stations involved in this project ranged from 4 months to 27 months with most stations falling between 13 and 24 months.

The Stage II systems tested for this project included balance systems and four varieties of vacuum-assist systems as shown in Table 1:

Table 1 - Types of Stage II Systems Tested
Type of System	Number Tested	Percentage of Total Stations Tested
Balance	6	19
Franklin Intellivac	1	3
Gilbarco Vapor Vac	8	25
Healy Systems with Model 600 Nozzle	2	6
Wayne Vac	15	47
Total	32	100

III. Results

A. Pressure Decay Testing

Pressure decay tests were conducted at all 32 stations that were part of this project. One station was not included in the analysis of the results because it was not comparable to the other 31 stations. The total number of system components tested included 90 underground storage tanks, 128 gasoline dispensers and 360 gasoline nozzles. The results of the initial test at each station are presented in Table 2. As the number of stations tested was relatively small, the results do not provide definitive evidence for how many months a station is likely to maintain compliance with the pressure integrity standard but it is interesting to note that the three stations that had been tested within approximately four months all passed the pressure decay test. The magnitude of pressure decay failures is depicted graphically in Figure 1.

Table 2 - Initial Pressure Decay Test Results
Number of Stations	Percentage of Total Stations
All Stations	31	100
Pass	10	32
Fail	21	68
Vacuum Assist Stations	25
Pass	10	40
Fail	15	60
Balance Stations	6
Pass	0	0
Fail	6	100

At most stations where the initial pressure decay test failed, more than one leaking component contributed to the test failure. It was not possible to determine the relative significance of leaking components in comparison to one another. Certain components were observed to be leaking more frequently than others (see Figure 2). The two components most frequently observed to be leaking, over all system types, were fill caps and Stage I poppet valves (dry breaks), both found to be a contributing factor in 41% of all the test failures. From the results of this testing, leaking nozzles were associated with test failures only at balance stations where 13 of the 56 nozzles tested were leaking. Leaking nozzles were a significant problem at balance stations where each of the six stations tested exhibited at least one leaking nozzle. The total number of components found to be leaking during this project are listed in Table 3.

Table 3 - Parts Found Leaking During Pressure Decay Tests
Part	Number Leaking	% Leaking out of Total Number Tested
Fill Cap	11	12
Fill Adaptor	9	10
Spill Bucket Drain Valve	12	not determined
Stage I Poppet Valve	15	27
In-Tank Monitor	3	not determined
Submersible Pump	1	1
Balance System Nozzle	13	23
Breakaway	3	<1

B. Vacuum Line Integrity Test

The vacuum line integrity test was performed at two stations equipped with the Healy Systems, Inc. system and using a central vacuum source. Both stations passed this test on the initial attempt.

C. Air to Liquid Ratio Test

The A/L ratio test was performed at a total of 26 stations and involved testing a total of 298 nozzles. Types of Stage II systems tested included Wayne Vac, Gilbarco Vapor Vac, Healy Systems, Inc. and Franklin Intellivac. Test results are presented by type of system in Figure 3. The results are broken down into the percent of nozzles tested that were within the allowable A/L ratio range and those within specified percentages of the allowable range. Nozzles that were not within the allowable A/L ratio range all exhibited low A/L ratios. For two of the system types, Healy Systems, Inc. and Franklin Intellivac, only a very limited number of systems were tested. The results indicate an 89% compliance rate when all vacuum-assist nozzles tested are grouped together regardless of type of system.

As part of the A/L ratio testing, the gasoline flowrates at each nozzle were also checked. The CARB executive orders specify an allowable range for the gasoline flowrate for each Stage II system. No flowrate can exceed 10 gallons per minute (gpm) and the lowest flowrate allowed can vary from 6 gpm to 7 gpm, depending upon the system, with 7 gpm being the most common. The 10 gpm maximum flowrate is also a federal requirement. Out of the 298 nozzles tested, 16 were observed to have gasoline flowrates outside the allowable range. Of these 16, 6 had flowrates that were in excess of 10 gpm and 10 had flowrates that were too low. For the purposes of this testing, a gasoline flowrate outside the acceptable range was not counted as an A/L failure unless the A/L ratio was also outside the acceptable range.

D. Effort Required to Attain Compliance with Performance Standards

In addition to documenting the causes of test failures, the testing technician performed repairs, adjusted equipment and replaced broken or worn components as necessary to bring stations into compliance.For greater than 50% of leaking components some minor maintenance, such as tightening, was sufficient to stop the leak. In other instances, the component needed to be replaced. At 15 of the 21 stations that initially failed the pressure decay test, replacement of one or more parts was required to bring the station into compliance. At the remainder, tightening of parts or other adjustments was sufficient to achieve a passing test. At all stations the technician was able to achieve a passing test after performing repairs or replacing worn or broken parts. Excavation was not required at any of the stations to achieve compliance with performance standards.

For stations exhibiting problems with A/L ratios, adjustment of the vacuum motor or replacement of nozzles resolved most of the problems. At one station, an A/L ratio failure for all three nozzles on one side of a dispenser appeared to be due to a problem with the vacuum motor.

Overall, the APCD paid for replacement parts at 19 stations with the total cost of the parts amounting to $6315.40. At a few stations, replacement parts were provided by the owners.

IV. Conclusions

Based on the results of this testing project it is apparent that a significant number of gasoline stations cannot pass a pressure decay test without ongoing maintenance. The pressure integrity of Stage II systems degrades over time and it is evident that most gasoline stations would not pass a pressure decay test by the time their five year retesting requirement comes due. Without interim maintenance, many of these stations would exhibit decreased pressure integrity for a lengthy period of time leading up to their retesting date. This indicates that greater emission control would be achieved with more regular system maintenance.

The A/L testing results indicate a much higher compliance rate with the A/L ratio performance standard.