California Air Resources Board 

Public Workshop 

Enhanced Vapor Recovery

ISD Alarms and Emissions

Related to Overpressure

November 6, 2015 in Sacramento

November 10, 2015 in Diamond Bar

1
Housekeeping

• Emergency Exits, Building Evacuation, Restrooms

• Hold questions and comments till end of each segment

• For those participating via conference call and webinar, 

email your comments during the presentation to 

george.lew@arb.ca.gov

• Presentation, webinar information, and conference call 

information is posted at 

http://www.arb.ca.gov/vapor/vapor.htm

2
Purpose of Workshop

• Discuss findings from ARB studies

• Present ideas for possible solutions

• Request input from interested parties

• Identify and resolve issues prior to proposing 

a regulatory solution to our Board

• Answer questions

3
Discussion Topics

• Background

• Review of previous analysis and findings

• Presentation of new analysis and findings

• Summary of major conclusions

• Presentation of solutions being considered

• Next steps

4
Background

5
Enhanced Vapor Recovery (EVR) and

In-Station Diagnostics (ISD) 

• Statewide ~ 7,500 gasoline dispensing facilities (GDF) are 

equipped with Phase II EVR and ISD

• ISD continuously monitors the performance of the vapor 

recovery system (VRS) and alerts the operator of 

potential equipment failures

• One of the ISD parameters involves continuous 

monitoring of pressure in the headspace of the 

underground storage tanks (UST)

6
ISD Overpressure (OP) Alarm Criteria

Assessment 

Period

Current ISD OP Alarm Criteria

Weekly 5% of UST pressure data above

1.5”WCG

(Section 9.2.4 of CP-201)

Monthly 25% of UST pressure data above 

0.5”WCG

(Section 9.2.4 of CP-201)

Daily Daily assessment to identify vapor 

processor malfunction

(Section 9.2.5 of CP-201)

7
Definitions

 ISD OP Alarm Problem: A situation in which the 

equipment inspection, testing, and 

troubleshooting conducted in response to an ISD 

OP alarm fails to identify an equipment 

malfunction

 OP Emission Problem: A situation in which the 

emissions resulting from positive pressure in the 

underground storage tank are of concern with 

regard to the regional ozone standard or near 

source risk due to benzene exposure

8
Why Are We Concerned?

1. False ISD Alarms

• Alarms require service provider response, yet no 

trouble is found in winter time

• Costly and disruptive for GDF operator

2. Air Quality Impacts

• Statewide ROG emissions from overpressure are 

estimated at 11 TPD winter and 1 TPD summer 

• Potential near source health risk issues at worst 

case sites due to increased benzene exposure

9
How Do Phase II Enhanced 

Vapor Recovery Systems Differ?

Assist Balance

% of GDF Population 60% 40%

Date Initially Certified September, 2005 April, 2008

Principal of Operation Active, requires vacuum 

pump in vapor return 

pathway

Passive, requires low 

resistance vapor return 

pathway 

Nozzle Vapor Pathway One way path, breathing 

losses from UST cannot 

occur

Two way path, allows 

breathing losses from UST 

to occur

10
Assist System: Pressure Driven 

Emissions

11
Balance System: Pressure Driven 

Emissions

12
Scope of OP Problem: Assist Systems

Severity of Overpressure Condition Estimated Population

( ~ 4500 sites, 60% )

Tier 1: No overpressure Alarms in December 

negligible pressure driven emissions. Little 

or no time at positive pressure.

Population: ~1035

(23% of assist sites)

Tier 2: Overpressure conditions which 

produced alarms in December, but an 

efficiency loss less than 5%. Positive 

pressure occurs during overnight idle period.

Population: ~1935

(43%, of assist sites)

Tier 3: Overpressure conditions which result 

in efficiency loss greater than 5% in winter 

months and/or potential concerns over 

elevated risk at the worst case sites. Positive 

pressure occurs for long periods of time 

during dispensing operations

Population: ~1530

(34% of assist sites)

13
South Coast Assist Site Pressure Comparison October and December

Ullage

Pressure

14
Scope of OP Problem: Balance Systems

Severity of Overpressure Condition Estimated Population

( ~ 3000 sites, 40% )

Tier 1: No overpressure Alarms in 

December negligible pressure driven 

emissions. No positive pressure during 

dispensing operations.

Population: ~ 300 

~10% of sites have high throughput 

Not expected to exhibit positive 

pressure while dispensing

Tier 2: Overpressure conditions which 

result in overpressure alarms and efficiency 

loss less than 5%. Exhibit slight positive 

pressure during dispensing operations

We expect that most of the remaining 

2700 sites will fall into tier 2, but further 

analysis is needed to estimate the 

number

Tier 3: Overpressure conditions which 

result in efficiency loss greater than 5% 

and/or potential concerns over elevated 

risk at worst case sites. Exhibit slight 

positive pressure during dispensing 

operations

We expect that only a small percentage 

of the remaining 2700 sites will fall into 

this tier, but further analysis is needed 

to estimate the number

15
South Coast Balance Site Pressure Comparison October and December

16
Causes of Overpressure

• Primary cause is uncontrolled Reid Vapor Pressure 

(RVP) of winter gasoline

• Secondary causes include:

– Type of Phase II EVR system installed (Assist or 

Balance)

– Excess air ingested when fueling vehicles equipped 

with on-board refueling vapor recovery (ORVR)

– Gasoline throughput

– GDF maintenance practices

– GDF operating hours

17
Review of Previous 

Analysis and Findings

18
Major Elements of OP Study

• Study Sites with Continuous Data Collection

• Vapor Recovery System (VRS) Performance Testing

• Reid Vapor Pressure (RVP) Sampling and Analysis

• Collection of ISD Alarm History, UST Pressure Data, 

and VRS Configuration from ~400 Sites

19
Study Sites with Continuous 

Data Collection

• Six sites in Northern California established 

Fall 2009

• Five sites in Southern California 

established Fall 2013

• Each equipped with “PV Zero” vent valve, 

barometric/UST pressure monitor, & ISD 

data acquisition system

• Data used to estimate pressure driven 

fugitive and vent line emissions

20
Vapor Recovery System 

Performance Testing

• Conducted at 15 Sites 

Exhibiting PWD

• ISD Operability

• Nozzle Bag Test

• CAS Integrity

• Vapor to Liquid (V/L) Ratio

• Dispenser Integrity

• System Pressure Integrity

21
22
Data Collected From ~400 Sites in Six 

Geographic Regions

- Collaborative effort between ARB and Districts

- 14 ARB staff members

- 28 District staff members

ISD Data

- All alarm history data available (at least one year)

- Available pressure and ullage data

- Available records on last 10 deliveries to gather 

available data on fuel temperature

- V/L data on for recent vehicle fueling events

GDF Characteristics

- Operating hours

- Throughput

- Gasoline brand and source

- Inventory report with tank capacities

23
Prevalence of OP Alarms: 

Data Set OP Alarms October 

2013

November 

2013

Assist Sites

(274)

Average Number of 

Alarms Per Site 0.16 1.84

% of Sites With at 

Least One Alarm 8.8% 69.7%

Balance Sites

(121)

Average Number of 

Alarms Per Site 0.02 0.36

% of Sites With at 

Least One Alarm 1.7% 19.8%

24
25
Presentation of New 

Analysis and Findings

26
Expected V/L Ratio During 

Refueling of ORVR Vehicles

• The assist nozzle is designed to reduce the V/L to < 0.5 

when refueling ORVR vehicles

• Air ingestion and vapor growth occurs inside UST when 

V/L > 0.5 on ORVR vehicles 

27
Assist System

ORVR Recognition

• Tier 3 sites (PWD) exhibit higher V/L when 

compared to Tier 2 and Tier 1 sites

• The ability of the assist nozzle to identify ORVR 

vehicles has declined over the last several years

• ORVR vehicle identification can vary within the 

same make, model, and model year

28
Assist Nozzle ORVR Recognition Study

• Conducted in January 2015, at six retail GDF located 

in San Diego region

• Total of ~ 1600 valid vehicle refueling observations, 

85% ORVR, 15% Non-ORVR

• Observed and recorded each vehicle refueling event 

followed by retrieval of V/L data from ISD 

29
ORVR Recognition Study Findings

• Percentage of ORVR vehicles with V/L ≥0.5 

(mis-identification rate) was 30%

• Percentage of ORVR vehicles with V/L ≥ 1.0 

was 18%

• Capless fill pipes represented 4% of data set, 

75% had a V/L ≥ 1.0

30
Trends in Assist Nozzle ORVR 

Mis-Identification Rate 

Healy Assist

Certification

Between 2004 and 2015, ORVR penetration 

increased from 24% to 84% at sites studied.

31
Differences in ORVR V/L

by Model Year

Model Year 

Duration

Number 

of ORVR 

Events

ORVR 

V/L

Number of 

ORVR Events 

with V/L Greater 

Than 0.5

Percent of 

ORVR 

Events with 

V/L Greater 

Than 0.5

2000-2011 838 0.49 222 27%

2012-2015 496 0.61 189 38%

32
ORVR Vehicle Refueling Experiment

( Summer 2015 )

Step 1: Remove existing fuel from 

ORVR vehicle of interest

Step 2: Dispense fuel under 

controlled conditions

Step 3: Record volume dispensed, 

vacuum generated, time, and vehicle 

information

Step 4: Retrieve ISD data, 

determine V/L ratio

33
Breakthrough/Key Finding

V/L can vary depending on whether nozzle is 

securely latched or loosely latched in the vehicle 

fill pipe

Item Description

5 Nozzle Latch Ring

C Fill Pipe Locking Lip

34
Secure Latch vs Loose Latch

Gap

Nozzle Secure Latch Nozzle Loose Latch

35
ORVR Vehicle Refueling Experiment 

August 2015 (Certified Nozzle)

Vehicle Make/Model Secure/Loose Latch

Nozzle Boot

(InH20) Avg V/L

Nissan Altima Secure -1.35 0.43

Nissan Altima Loose 0.00 1.10

Toyota Corolla Secure -1.74 0.24

Toyota Corolla Loose 0.00 1.09

Toyota Prius C Secure -1.48 0.25

Toyota Prius C Loose 0.00 1.14

Honda Civic Secure -1.37 0.46

Honda Civic Loose N/A * 0.49

*Vacuum needle came loose during fueling

36
ORVR Vehicle Refueling Experiment

September 2015 (Prototype Nozzle)

Vehicle Make/Model Secure/Loose Latch*

Nozzle Boot

(InH20) Avg V/L

Nissan Altima Secure -0.96 0.21

Nissan Altima Loose - -

Toyota Corolla Secure -1.57 0.18

Toyota Corolla Loose - -

Toyota Prius C Secure -1.48 0.19

Toyota Prius C Loose - -

Honda Civic Secure -0.85 0.27

Honda Civic Loose - -

*Loose latch not possible

37
ORVR Vehicle Refueling

Experiment Conclusions

• ORVR vehicle mis-identification can vary within the 

same vehicle make, model, and model year

• ORVR vehicle mis-identification issue appears to be 

related to two potential causes:

– Engagement of nozzle “latch ring” with fill pipe 

“locking lip” (loose latch vs secure latch)

– Vehicle fill pipe design (open path to atmosphere)

• Prototype nozzle performed well, FFS pleased with 

results and will establish R&D test site

38
Questions Regarding

Balance System

• Although balance systems don't experience a 

high frequency of overpressure alarms, they 

operate at slightly positive pressure for ~ 25% of 

time with winter fuel and ~ 13% of the time with 

summer fuel

• Is outward flow (reverse flow) at the nozzle 

preventing the overpressure alarm from 

occurring?

• If so, should we be concerned about these 

emissions?

39
City

Hours of 

Operation

Thoughput

kgal/mo

% of 

Data 

Points 

Greater 

than 

Zero in 

Oct.

% of 

Data 

Points 

Greater 

than 

Zero in 

Dec.

Avg of 

Data 

Points 

Greater 

than Zero 

Oct.

Avg of 

Data 

Points 

Greater 

than Zero 

in Dec.

Diamond Bar 24 Hr 100 19.5% 34.4% 0.27 0.16

Ontario 24 Hr 110 15.9% 17.6% 0.27 0.20

Chino 24 Hr 110 7.4% 31.8% 0.35 0.24

Stanton 24 Hr 115 21.6% 36.5% 0.17 0.17

Yorba Linda Closed Nightly 116 24.7% 28.2% 0.10 0.25

Brea 24 Hr 119 16.2% 32.2% 0.08 0.22

Chino 24 Hr 125 17.7% 19.4% 0.27 0.14

La Habra 24 Hr 128 23.8% 27.2% 0.34 0.21

Bellflower 24 Hr 132 10.6% 18.5% 0.20 0.07

Sun City Closed Nightly 133 12.4% 23.4% 0.05 0.18

Costa Mesa 24 Hr 143 15.9% 32.0% 0.14 0.82

Ontario 24 Hr 150 8.2% 25.7% 0.08 0.23

Long Beach 24 Hr 151 14.5% 29.3% 0.20 0.11

Stanton Closed Nightly 154 13.8% 25.9% 0.41 0.07

Stanton 24 Hr 155 1.4% 15.9% 0.17 0.36

Murrieta 24 Hr 160 2.9% 19.1% 0.12 0.13

City of Industry 24 Hr 160 19.8% 28.2% 0.02 0.27

Los Angeles 24 Hr 161 4.3% 30.8% 0.03 0.14

Hollywood 24 Hr 165 14.9% 32.2% 0.26 0.23

Burbank 24 Hr 170 22.6% 20.2% 0.21 0.45

Bellflower 24 Hr 170 15.5% 27.3% 0.27 0.22

Garden Grove 24 Hr 180 8.0% 25.7% 0.22 0.16

Santa Monica 24 Hr 200 5.2% 13.0% 0.05 0.17

Yorba Linda 24 Hr 203 17.5% 28.2% 0.34 1.08

Santa Ana 24 Hr 205 12.0% 19.1% 0.13 0.23

Diamond Bar 24 Hr 250 4.0% 17.0% 0.08 0.24

Ontario 24 Hr 280 9.8% 21.0% 0.12 0.13

Average 13.3% 25.2% 0.18 0.26

Std Dev. 6.62% 6.34% 0.11 0.22

Minimum 1.4% 13.0% 0.02 0.07

Maximum 24.7% 36.5% 0.41 1.08

40
Primary Objectives of

Balance System Testing

• Determining if the release of vapors through 

the balance nozzle explains the difference in 

frequency of overpressure that is observed at 

GDF with balance systems vs GDF with assist 

systems

• Determine the mass of vapor that can be 

emitted when UST is held at a slight positive 

gauge pressure (0.1 to 0.3 “WCG)

41
Balance System Testing

( July 2015 )

• Phase II efficiency testing conducted on 60 cars 

under normal operating conditions to establish 

baseline, then on 200 cars at slightly positive UST 

pressure

• Both VST and EMCO nozzles tested

• Pump used to bubble air through liquid gasoline 

at bottom of underground storage tank

• Pressure switch used to turn pump on at pressure 

below 0.1 “WCG and turn pump off at pressure 

above 0.3 “WCG

42
Balance System Testing

43
Slight UST Pressure Results in Reduced 

Nozzle Collection Efficiency and Higher 

Emissions During Fueling Events

44

# of 

Events

Dispensed 

Gasoline 

Volume

(gallons)

Efficiency Loss 

Based on UEF

= 7.65 lb/kgal

Dispenser

VR Line Pressure

("WCG)

Ave. Max. Min.

Baseline ORVR Events 30 386 0.5% -0.64 -0.16 -1.14

Baseline Non- ORVR Events 30 409 1.9% -0.44 0.00 -1.00

Pressurized ORVR Events 99 1246 10.5% 0.15 0.22 0.09

Pressurized Non- ORVR Events 96 1471 25.4% 0.19 0.29 0.09
45
Balance System Testing Conclusions

• Pressure driven emissions from balance systems are 

on the same order of magnitude as pressure driven 

emissions from assist systems

• The outward flow through the balance nozzle is 

sufficient to release the vapors produced by 

evaporation in the UST 

• This is the reason that the balance systems exhibit 

lower UST pressures and fewer overpressure alarms 

than the assist systems

46
Summary of 

Major Conclusions

47
• OP is driven by RVP and is primarily a winter problem

• Current pressure based ISD alarm standards can be 

more stringent than needed to ensure acceptable 

system performance

• Poor seal at ORVR fill pipe a major contributor

• Both balance and assist systems are affected

• Emission estimates characterize extent of problem:

– Regional Basis (Ozone AAQS) : Minor impact 1 ton per day 

statewide in summer months

– Site Specific Basis (Benzene Risk): Potentially significant at 

worst case sites. Statewide 11 tons per day in winter 

months

Major Conclusions

48
Presentation of Solutions

Being Considered

49
Potential Solutions

1. Address loose latch problem on assist nozzles to 

lower air ingestion and on balance nozzles to 

reduce emissions at positive pressure

2. Revise ISD alarm thresholds to be emissionbased rather than pressure-based

3. Certify high capacity processors capable of 

handling worst case vapor production caused by 

evaporation

4. Adopt new vehicle fill pipe performance 

standards to ensure new model ORVR vehicles 

and EVR nozzles control V/L to less than 0.5

50
Address Loose Latch Problem

• Ensure that fuel cannot be dispensed unless a 

good seal is made between nozzle and vehicle

• Relatively low cost for nozzle spout kit

• Assuming natural turnover, 4 years for 100% 

implementation

• Lower ORVR V/L will reduce UST pressures and 

pressure driven emissions

51
Emission-Based ISD Alarm Criteria

Current ISD Threshold Proposed ISD Threshold

Percentage of time at 

pressure:

• 5% of time greater 

than 1.5 ”WCG over 

seven days

• 25% of time greater 

than 0.5 ”WCG over 30 

days

Summer: Efficiency loss due

to pressure driven losses

Year Round: Emission rate 

to limit health risks due to 

benzene

Estimated cost of implementing revised alarm criteria $5,500 per site

52
High Capacity Processors

• Costs $12K to $50K per site depending on the 

processor system chosen 

• Could completely eliminate pressure driven 

emissions regardless of all other factors (GDF 

parameters, vehicle fleet, fuel RVP etc.)

• Only needed at sites which continue to have 

overpressure emission alarms with new 

criteria

53
New Vehicle Fill Pipe 

Performance Standards

• Required to ensure nozzle vehicle 

compatibility into the future

• Necessary since vehicle designs change on a 

frequent basis

• Long implementation time frame since vehicle 

lives are greater than 10 years 

• Does not address incompatibility associated 

with earlier model year vehicles

54
Next Steps

55
Further Analysis Planned

• Study loose latch prevalence in balance nozzles

• Download ISD data from ~400 sites to check current 

alarm and PWD trends

• Evaluate performance of improved nozzles & high 

capacity processors 

• Assess health risk issues

• Develop amendment for ORVR vehicle fill pipe 

standards 

• Estimate effectiveness and cost of each proposed 

solution

56
Next Steps

• Field testing of potential solutions (new nozzles and 

high capacity processors)

• Review and refine emission estimates

• February 2016 - Informational update to the Board

• Spring 2016 - Workshop on effectiveness of proposed 

solutions

• Summer 2016- Workshop on proposed regulatory 

language

• Late in 2016- Propose regulatory amendments to the 

Board

57
Contact Us

Lou Dinkler

louis.dinkler@arb.ca.gov

John Marconi

john.marconi@arb.ca.gov

Gurj Bains

gurjeet.bains@arb.ca.gov

58