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                                                  EPA/600/4-87/016
                                                       May 1988
      SURVEY OF VENDORS OF EXTERNAL
    PETROLEUM LEAK MONITORING DEVICES
FOR USE WITH UNDERGROUND STORAGE TANKS
                        by

                     B. Eklund
                       and
                      W. Crow
                  Radian Corporation
                  Austin, Texas 78766
               Contract No. 68-02-3994
                    Project Officer
                   J. Jeffrey van Ee
             U.S. Environmental Protection Agency
          Environmental Monitoring Systems Laboratory
                Las Vegas, Nevada 89114
     ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
          OFFICE OF RESEARCH AND DEVELOPMENT
         U.S. ENVIRONMENTAL PROTECTION AGENCY
               LAS VEGAS, NEVADA 89114

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                                        Contents

Section                                                                                 Page

    Executive Summary	v

1   Introduction	1-1
    1.1 Background	•	1-1
    1.2 Program Objectives	1-2
    1.3 Scope of Work and Report Outline	1-2
    1.4 Overview of Leak Detection and Tank System Design	1-2
       1.4.1  Leak Detection	1-2
       1.4.2  Tank System Design	1-3

2   Conclusions and Summary of Results
    2.1 Conclusions	2-1
    2.2 Summary of Results	2-1
       2.2.1  Summary of General Findings for Monitoring Systems .  .  .	2-1
       2.2.2  Summary of Findings for Intermittent Liquid-Phase Detectors	2-1
       2.2.3  Summary of Findings for Continuous Liquid-Phase Detectors	.  . 2-1
       2.2.4  Summary of Findings for Intermittent Gas-Phase Detectors	2-2
       2.2.5  Summary of Findings for Continuous Gas-Phase Detectors	2-2

3   Technical Approach
    3.1 Literature Search	3-1
    3.2 Vendor List	3-1
    3.3 Vendor Survey	3-1

4   Results
    4.1 Discussion of Survey	4-1
    4.2 Tabulated Results From Survey	4-1
       4.2.1  Principle of Operation	  4-1
       4.2.2  Other Results	4-12
    4.3 Evaluation of Results	4-12
       4.3.1  Performance Categories of Leak Monitoring Techniques	4-12
       4.3.2  Site-Specific Factors	4-23
    4.4 Discussion of Results	4-23
       4.4.1  Overall Results	4-23
       4.4.2  Questionnaire Results	4-26

5   References	5-1

6   Bibliography
    6.1 Selected Bibliography	6-1
    6.2 Additional Citations Identified in Literature Search	  6-2

Appendix  A - List of Vendors	'	A-1

Appendix  B - Questionnaire Format	B-1

Appendix  C - Tabulated Survey Results	 . . C-1

G  Glossary of Terms	G-1

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                                          Tables
Number                                                                                 Page
1    Characteristics of Leak Detection Sensors	vii
4-1    List of Vendors and Response to Survey	4-2
4-2   Commercially Available Leak Monitoring Techniques	4-5
4-3   Detection Specificities of Various Leak Monitoring Techniques	4-14
4-4   Detection Capabilities of Various Leak Monitoring Techniques	4-15
4-5   Experience of Various Leak Monitoring Techniques	4-17
4-6   Costs for Various Leak Monitoring Techniques	4-19
4-7   Recommended Procedures for Various Leak Monitoring Techniques	4-20
4-8   Effect of Site-Specific Factors and Design Options on Selection of Leak Detection Methods .  . 4-24
4-9   Relative Advantages/Disadvantages of Leak Monitoring Techniques	4-25
4-10  Summary of Available Test Procedures and Results for Leak Monitors	4-27

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                                           Figures
Number                                                                                 Page
1-1   Elements of an Underground Storage Tank Installation	1-4
1-2   Example of Observation Well Installation	1-5
1-3   Example of Vapor Monitoring Well	1-6
4-1   Bailer Used for Grab Sampling	4.5
4-2   Schematic of a Radiation infrared (IR) Detector	4-6
4-3   Schematic of a Photoionization Detector (PID)	4-6
4-4   Schematic of Leak Monitoring System Using Product-Soluble Pressurized Tube	4-7
4-5   Schematic of Mechanically Activated, Product-Soluble Device	4-9
4-6   Schematic of Electrically Activated, Product-Soluble Device	4-10
4-7   Schematic of Electrical Resistivity Sensor Coated With Product-Soluble Polymer	4-11
4-8   Schematic of Typical Installations of Thermal Conductivity Sensor	4-12
4-9   Schematic of Product-Permeable Device	4-13
4-10  Decision Tree for Detector Classification	4-23
                                              IV

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                                    Executive Summary
Underground storage  tanks (USTs)  and their
associated piping  are major potential sources of
environmental contamination.   Since the 1984
Amendments to the Resource Conservation  and
Recovery  Act  (RCRA)  require  regulation of
underground storage  tank systems, the  U.S.
Environmental Protection Agency (EPA) is currently
investigating topics related to USTs to aid in
developing regulations.  EPA has  contracted with the
Radian Corporation to compile information on the
various types of external (out-of-tank)  monitoring
systems or techniques which can be used to detect
leaks or spills of petroleum hydrocarbon products. The
compiled  data were  used to categorize  external
petroleum leak monitoring  devices or techniques by
function and type, and the data will aid in the future
development of performance criteria for commercially
available  external leak  monitoring  methods.  The
present study was conducted in 1986 and is  limited to
external (outside-the-tank)  petroleum leak monitoring
devices.  It supports the EPA effort  by providing
information on the number, type, and performance
capabilities of available leak monitors.

The literature was searched to collect general
information on external petroleum leak monitors and,
more  specifically, to develop  a list of vendors.
Additional information was collected  from equipment
vendors, trade groups,  and other researchers.  A
questionnaire soliciting information on leak monitoring
devices was developed and sent to the identified
vendors.   The  questionnaire covered  six topics:
principle of operation, detection specificity,  detection
capability, experience, cost, and recommended
procedures. The vendor list included vendors of UST
monitoring  systems and  detectors that could
potentially be used for  the detection  of petroleum
hydrocarbon  leaks or spills.  It should be noted that
this survey does not necessarily represent a complete
list of vendors that manufacture external monitors for
detecting petroleum leaks or spills from underground
storage tanks and piping.  Some  vendors were  likely
to have been inadvertently omitted, and devices that
are currently being marketed could have  changed
since this survey was performed.  However,  these
data will be useful in identifying the different
categories of commercial leak monitoring devices and
aiding in the  development  of performance criteria for
each monitoring category.  This  report summarizes
and tabulates vendor responses to the questionnaire.
The report also includes a discussion of related issues
that remain to be resolved before final performance
criteria can be established.

The data collection approach used in this study has
limitations.  Reliance on vendor-supplied data was
necessary because of a  lack of published, objective
evaluative test results. However, since these vendor
data  have not been  independently verified, it is
possible that  some of these data  are erroneous,
biased, or self-serving.

The literature search yielded relatively little useful
information on external leak detection  monitoring
devices.  The vendor survey, however, was successful
in gaining information from approximately 70 percent
of the vendors that were queried. Except for a notable
lack of data regarding  any common interference,
operational,  or  maintenance problems,  vendor
responses were generally thorough.

A total of 49 vendors was identified that manufacture
devices  related to the out-of-tank measurement of
petroleum hydrocarbon  spills or  leaks from UST
installations.  Vendor specifications were received for
63 of 69 (91 percent) different products. Survey forms
were completed by 30 of the 42 vendors that were
queried.  Survey forms were received for 44 of the 62
(71 percent) devices covered by the survey.

Vendor responses provided a basis for dividing the
external  (out-of-tank)  leak monitoring devices for UST
systems into four categories: intermittent liquid-phase
detection,   intermittent gas-phase  detection,
continuous liquid-phase  detection,  and continuous
gas-phase  detection.  An examination of vendor
survey datr, yielded the following information:

   o Commercial external (out-of-tank) leak monitors
    are designed primarily to detect leaks or spills of
    petroleum hydrocarbons;
   o Most leak monitoring systems cannot immediately
    distinguish between surface spills and leaks;
   o Most leak monitoring devices do not measure leak
    rates, although some devices (gaseous detectors)
    are capable of measuring hydrocarbon
    concentrations;

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  o No uniform performance specifications exist for
    external leak monitoring devices;
  o Most leak monitoring systems require the
    installation of observation wells or boreholes;
  o Vendor responses were limited with regard to:
    - Operational problems,
    - Interferences,
    - Maintenance problems, and
    - Performance testing procedures;
  o Most leak monitoring systems can be retrofitted at
    existing LIST installations;
  o Intermittent monitoring techniques are more labor-
    intensive than continuous techniques, but may be
    more reliable;
  o Gas-phase detection can be more sensitive than
    liquid-phase alarms and subject to interferences;
  o Equipment and installation costs (for permanent
    external  leak detection systems) may vary
    considerably, as these costs are dependent on the
    type of devices selected and the number of
    sensors used in each installation, local
    construction codes and permitting costs, and local
    labor costs; and
  o Operational and maintenance costs for permanent
    external leak monitoring systems may also vary,
    but are thought to be low, on the basis of
    information obtained from equipment vendors.

The performance characteristics for each leak
detection category  are  summarized  in Table  1.  The
data presented in Table 1 are based on information
obtained from vendors  and have not been verified by
independent testing; therefore, these data may be
biased.
                                                  vi

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                 Table 1
Characteristics of Leak Detection Sensors*
                 Leak Detection Category

Type of Compounds
Detected
Detection Adjustable
for Specific
Compounds
Potential
Interferences
Severity of
Interferences
False Positives or
Negatives
Temperature Range
Can Systems Be
Retrofitted?
Are Wells Required?
Can Devices Be
Used in Wet Soils?
Years on Market
Detection Limits
I Lower
1
Upper
1 Response
1 Characteristics
1 Lag Time
Rise Time
Fall Time
Drift
Precision
Intermittent
Liquid-Phase
Liquid hydrocarbons
Generally not
None
Low
Unlikely
>0°C
Yes
Yes
Yes
>5

1/64 to 1/32 in.
None

N/A
N/A
N/A
N/A
N/A
•NOTE: The information presented in this table
not on actual performance data which has been
**LEL - Lower Explosive Limit
Continuous
Liquid-Phase
Vapor/liquid
hydrocarbons
Generally not
Physical and
chemical
Variable
Unlikely
-45to120°C
Yes
Usually
Yes
0-15

1/32 to 1/8 in.
None

1 sec. to 10 hr.
1 sec to 60 sec.
1 sec. to ?
N/A
Unknown
is based on information
independently verified.
Intermittent
Gas-Phase
Hydrocarbon
vapors
Varies between
techniques
Chemical
Potentially high
Both possible
-20to60°C
Yes
Usually
Yes
2-10

0.1 to 1500ppm
2000 ppm to
100%LEL"

1 sec.
3 sec. to 30 sec.
5 sec. to ?
Negligible to
<1%/day full scale
5% to unknown
provided by vendors of
Continuous II
Gas-Phase ||
Hydrocarbon II
vapors I
Generally not II
Chemical II
Potentially high
Both possible
-70 to 70°C
Yes
Usually
Yes
0-20

1 0 to 1 00 ppm
1%to
100%LEL"

1 sec. to 10 min.
1 sec. to 20 sec.
20 sec. to several
minutes
Negligible to
<1%/day full scale
5% to unknown
monitoring devices and
                     vii

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                                         SECTION 1
                                        Introduction
1.1  Background

Underground storage  tanks (USTs) and their
associated piping represent a major potential source
of environmental contamination.  If not detected, leaks
of stored petroleum hydrocarbons can migrate through
the soil and can contaminate ground-water supplies.
Petroleum product leaks can accumulate underground
and can result in an explosion or in exposure hazards
that are due to the migration of volatile organic vapors
through  the soil into basements, sewers, and utility
vaults. Of the estimated 3 to 5 million underground
hazardous substance storage tanks currently in the
United  States, 1.4  million  are  used  to  store
gasoline1.2.   As  many  as one-quarter  of  the
underground (steel) storage tank systems (tanks and
piping) may be leaking3.   More than 95% of all tank
leaks are caused  by  the  corrosion  of  steel
components, with tanks over 10 years old  being the
most susceptible to corrosion4. Leaks in piping are
commonly due  to one of several factors, including
corrosion, faulty  installation,  accidents, and
environmental stresses (such as frost  heaves).  The
problem  is  particularly  acute  because  most
underground  tank systems are  made of unprotected
steel and are an average of 12 years old. Several
major oil companies have sought  to  minimize
environmental  effects from leaking underground
storage tanks by systematically  replacing existing
tanks and piping with  new  corrosion-resistant
fiberglass  or fiberglass-reinforced plastic  (FRP)
systems, FRP-clad steel tanks, or  with coated and
cathodically protected steel tanks.  However, the large
number of tanks in existence, as well as several well-
publicized leaks, has prompted Congress  to include
the regulation of underground storage tanks under the
Resource Conservation and Recovery Act (RCRA).

Subtitle I of  the 1984 Hazardous and Solid  Waste
Amendments to RCRA  requires that  the U.S.
Environmental Protection Agency (EPA) establish a
comprehensive program for the regulation of new and
existing underground storage tanks. Specifically, this
law requires that  federal and state regulatory
programs include "requirements for maintaining a leak
detection system, an inventory control system together
with tank testing, or a comparable system  or method
designed to identify releases in a manner  consistent
with the protection of  human  health and the
environment"6.  The law covers underground storage
tanks holding all  substances regulated under the
Comprehensive    Environmental   Response,
Compensation, and Liability Act (CERCLA) as well as
petroleum products (except for  hazardous waste
storage tanks already regulated under Subtitle C of
RCRA).

The U.S.  EPA has  established the  Office of
Underground Storage Tanks to oversee the regulatory
effort for controlling UST system leaks.  The EPA has
initiated work to estimate the number of tank systems
currently leaking, to evaluate tank  and piping integrity
(tightness) tests and  other inside-the-tank leak
detection methods, and to evaluate out-of-tank  leak
monitoring methods.  The Environmental Monitoring
Systems Laboratory  (EMSL) of the U.S.  EPA  in Las
Vegas is responsible for developing the technical
background necessary for developing regulations for
leak monitoring. A project team consisting of several
contractors assembled by EPA-EMSL  will perform a
number of functions  including:  collection  and
evaluation of user and vendor data, determination of
typical background soil contamination  levels, and
examination of transport mechanisms for vapor and
liquid pollutants.

Radian Corporation, under EPA Contract No.  68-02-
3994, is  assisting  EPA-EMSL in developing
performance criteria and certification procedures for
commercially available  external petroleum  leak
monitoring methods.  This, document  reports the
findings from  a survey of vendors of out-of-tank leak
monitors using a standardized questionnaire.  The
information compiled on the number, type, and
performance  capabilities of available leak monitors
may be used later to establish performance standards
and certification procedures.
 1.2  Program Objectives

 The primary objectives of the Phase I study were to:

   o Classify out-of-tank leak detection sensors for
    petroleum hydrocarbons by function and type
    and establish performance categories for each
    classification group of leak detection devices;
                                                1-1

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   o Identify ranges for performance categories
    applicable to each classification of petroleum
    hydrocarbon leak detection by using vendor-
    supplied data; and

   o Provide input to future development of
    procedures for certifying the performance of
    petroleum hydrocarbons out-of-tank leak
    detection sensors.

 This document serves as a background reference on
 external leak monitoring.  It is not a guidance manual
 for selecting an external leak monitoring device for
 LIST  systems.  Rather  it attempts to provide an
 introduction to the topic and to give an underground
 storage tank owner the necessary background to ask
 pertinent questions, seek more information, and assist
 the owner in making an informed choice.

 1.3  Scope of Work and Report Outline

 To meet the  objectives of  this study,  a four-step
 program was performed. First, a literature search was
 conducted to identify  relevant sources.  From these
 sources,  a list of vendors was developed.  The third
 step   involved  developing  and  mailing  out
 questionnaires to identified  vendors to solicit
 information on leak monitoring devices. The fourth
 step involved collecting and evaluating these data and
 reporting the findings.  Although an attempt was made
 to identify and communicate with as many vendors as
 possible, the resultant vendor list was not all-inclusive.
 Furthermore, no attempt was made to verify the claims
 made by the manufacturers or to limit the survey to
 "proven" UST leak monitors.

 Conclusions and a summary of results are presented
 in Section 2. Section 3  provides a discussion of
 pertinent issues such as  network design and data
 analysis.  The technical approach is described in more
 detail in Section 4. Section 5 presents the results of
 the Phase I work. Section 6 lists the references cited,
 and Section 7 contains  a bibliography.  Supporting
 data are given in the appendices. Appendix A lists the
 products,  technical  representatives, telephone
 numbers,  and addresses of the particular vendors.
 Appendix  B contains  a  copy of the vendor survey
 questionnaire.

 1.4  Overview of Leak Detection and Tank
     System Design

The following discussion  provides a brief overview of
underground storage tank systems and practices.  It is
 intended for individuals unfamiliar with these topics.
 Readers are encouraged to consult the publications
listed in  the bibliography in Section 6 for more
 information. When leak detection devices are chosen
 for a given underground installation, it is important to
 consider site-specific factors and  the  equipment
 chosen for each system component.  The following
 discussion provides background information about the
 generic types of equipment available for underground
 storage tank systems.

 1.4.1   Leak Detection

 A variety of programs can be followed to detect leaks
 or spills from underground storage tanks and piping
 including:  inventory control, tank and line integrity
 testing, and leak monitoring. Leak monitoring includes
 interstitial monitoring of double-walled tanks, areal
 surveillance, and use of observation wells  in the
 backfill material.  This report covers in detail only the
 last category of leak monitoring techniques.  Other
 programs and  types of leak monitoring are  briefly
 discussed below.

 1.4.1.1 inventory Control  Inventory control typically
 involves daily  measurements of volume of  stored
 product in each tank and monthly reconciliation of the
 current tank volume to the input and output records.
 Volume checks are  made either manually by using a
 gauge stick or automatically  by using an electronic
 level monitor. Detailed recommendations for inventory
 control procedures have been set forth by the EPA?
 and the American  Petroleum Institute8. Inventory
 control, which can detect large leaks, makes good
 business sense.  However, since this technique may
 not be accurate enough to satisfy the more stringent
 state and local leak detection  regulations, it is often
 used in conjunction with integrity testing or leak
 monitoring programs.  Electronic  inventory control
 systems  improve the accuracy of this technique to
 detect leaks from underground storage tanks and
 associated piping.

 1.4.1.2 Integrity Testing   Integrity (tightness) testing
 of  tanks and  pipes  involves  a  point-in-time
 determination of whether leaks are present in an
 underground storage tank system.   The tests fall into
 two general categories:  quantitative  and qualitative
 tests  (sometimes called volumetric  and  non-
 volumetric).  Either  type of test requires  the use of
 specialized equipment and may require shutdown of
 the facility  for up to a  full  day.  Most  current
 regulations specify that a quantitative rather than a
 qualitative integrity test be performed.

 Quantitative tests measure leak rates.  These tests
 monitor changes in product volume by measuring
 parameters  associated with volume changes
 (including changes in  liquid level, temperature,
 pressure, and density).  A  number of factors such as
temperature stratification within the tank, tank
                                                 1-2

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deformation, vapor pockets, etc., may obfuscate the
test results.  It is important to use trained test
operators who are experienced in identifying and
correcting for common test interferences.  The current
industry recommended practice, as specified by the
National  Fire Prevention Association  (NFPA), is the
ability to measure a leak rate of 0.05 gal/hr in tanks of
less than 12,500 gallons. The validity of this standard
and the ability of various test methods to  meet this
standard  are currently being investigated by the EPA.

Qualitative tests, which involve monitoring  either the
sounds  associated with leaking product or the
diffusion  of a tracer gas (e.g., helium) introduced into
the tank, determine the presence of  leaks.  These
tests do not quantify leak rates. Qualitative tests are
not necessarily  less sensitive than the  quantitative
tests.  The underlying assumption  is that  since any
leak can be significant over time, determination of a
leak rate is not necessary. The most prevalent type of
qualitative test uses helium as a tracer. One limitation
of this type of test is that the tracer gas is a smaller
molecule than the stored product, and  it  may pass
through fittings or other openings that are  liquid-tight.

1.4.1.3 Leak Monitoring   Interstitial monitors, used
with  double-walled  underground storage tanks,
monitor for fluid  or pressure changes.  Some external
continuous leak monitoring systems can be adapted
for use as interstitial monitors.

Area-wide surveillance methods include  a  number of
different approaches and techniques.  Their typical
application is mapping  contaminant plumes from
spilled hydrocarbons, but they can also be used for
leak monitoring. Included in this category are soil core
analysis, soil gas analysis, dyes and tracers methods,
surface geophysical techniques,  monitoring well
 networks, and other miscellaneous techniques.

 1.4.2   Tank System Design

 Figure 1-1 illustrates a typical underground storage
tank system.  Although underground storage tank
 systems have  a  number  of features  in common,
 several  major design options or site characteristics
 must be considered when  evaluating leak detection
options.  Section 4 discusses the effects of the various
design  options on the  selection of a monitoring
 approach.

 1.4.2.1  New Versus Old System   The best time to
develop a leak detection program is concurrently with
the selection  of tanks and associated piping.  This
 allows the system designer maximum  flexibility.
Considerations include providing a sufficient number
of tank openings for potential use of level detectors or
 integrity test equipment, or providing for  monitoring
with observation wells.  Existing UST systems offer
the designer fewer options.  For example, it is
normally prohibitively expensive to retrofit secondary
containment.  For many existing tanks, implementing a
periodic integrity test schedule and using inventory
control may  be preferable to retrofitting for leak
monitoring capability.

1.4.2.2  Tank and Piping Type  Two tank materials
are most commonly used: steel and fiberglass.  Each
is capable of adequate performance under the proper
conditions.  Since  corrosion is the  most common
cause of leaks in steel tanks, older, unprotected steel
tanks in corrosive soils are most at risk  and are the
most likely to benefit from an integrity test/leak
monitoring program.  At new steel tank installations,
the tanks should be coated and cathodically protected.
Other types of tanks that are protected from corrosion
include FRP and composites.  The composite  tanks
have a steel inner tank with a thick external coating of
FRP.

Piping  has been built in the past with carbon or
galvanized steel. Coated and cathodically protected
steel piping and FRP piping are now commonly used
at new installations.

1.4.2.3 Secondary Containment   Several types of
secondary containment have been used in UST
systems: double-walled  tanks, clay liners, concrete
vaults,  and synthetic liners.  The use of secondary
containment is advisable  for environmentally sensitive
areas.  Secondary containment prevents leaked
product from migrating out of the  near-tank area
before remedial measures can be taken.

A double-walled tank is  a tank within a tank, with  a
small  enclosed space separating the two.  It is  a
 relatively simple matter to monitor the annular  space
between tanks for leaks.  External leak detection (e.g.,
observation  wells) and integrity testing are  not
 normally necessary for double-walled tanks.

 Liners usually consist of a rubber  or polymer
 membrane that lines the tank or piping excavation.
Tanks and piping are placed in the hole and backfilled.
 Observation wells are typically placed within the lined
 hole to allow leak detection.

 Concrete vaults around USTs are mandatory in some
 states under certain conditions.  Since concrete is not
 an impenetrable barrier to product liquid and vapor
transport, it should be lined or coated.

 1.4.2.4 Overfill  Protection   The area around
 underground storage tanks can become contaminated
from the accumulation of small surface spills. The
                                                 1-3

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TANK TRUCK
                                    OVERFILL PREVENTION DEVICE    fi\

                                                       VAPOR RECOVERY LINE
                                                                                           PRODUCT
                                                                                           DISPENSER
                                                                   CORROSION-RESISTANT
                                                                   STORAGE TANK
                                                                                          AUTOMATIC
                                                                                          SHUTOFF
                                                                                          VALVE
                                                                        PRODUCT DELIVERY LINE
        MATERIAL
                                             LEAK DETECTOR

                                T) SUBMERGED PUMPASSEMBLY
      Well designed underground storage systems usually contain the following:
      (1) corrosion resistant tank;  (2) striker plate under tank fill line;  (3) submerged pump with leak detector on product
      delivery line; (4) float vent valve in tank vent line; (5) excavation walls and floor of impervtaus material; (6) asphalt or
      concrete excavation cap; (7) automatic shutoff valve on delivery line at pump island; (8) overfill prevention device at
      fill line on tank truck; (9) vapor recovery in tank truck during filling operation; (10) observation wells located inside
      excavation boundaries; (11) pea gravel or sand fill for excavation.
      These are all important aspects of a good underground storage system.


                                               Figure 1-1
                         Elements  of an Underground  Storage Tank Installation^
major cause of such spills is overfilling the tank during
liquid  transfer operations.   This problem can be
minimized by using in-tank  level  sensors, dry
couplings on transfer lines, or catchment basins
around fill pipes.   In installations without overfill and
spill prevention systems,  it  may  be difficult to use
vapor sensing devices for leak monitoring because of
the build-up over time of high background levels of
vapor  in the soil.  This  problem  may be overcome
through the  use of compound-specific tracers  to
assess tank system integrity.

1A2.5 Dry Versus Wet Excavations    Most UST
installation excavations are dry holes.   However,  in
areas of high groundwater, the hole may be wet some
or all of the time.  In wet-hole systems, external leak
detection  systems that detect liquid product and that
can differentiate between petroleum hydrocarbons and
                                             water are preferred.  Also,  because the water in the
                                             hole may enter the tank, the leak detection system can
                                             be augmented by monitoring the water layer in the
                                             tank as part of inventory control.  Site geology, other
                                             than  ground-water levels, should not significantly
                                             affect the selection of a leak monitoring system if the
                                             leak monitor is placed in the porous backfill material.

                                             The type of leak monitoring collection system used
                                             depends on the depth to groundwater and on the local
                                             variability in ground-water level. Some industry trade
                                             groups currently recommend using two observation
                                             wells per excavation for areas of shallow groundwater
                                             (or one well and secondary  containment) as in Figure
                                             1-2.  For areas with deep groundwater, vapor wells
                                             may be used to monitor for leaks as depicted in Figure
                                             1-3.
                                                   1-4


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 Well Outside
Tank Excavation
                                                                       Finished Grade
                                                                Well In Tank
                                                                Excavation
              Grout I
               Seal I
                                         Waterproof Caps
                                         Capable of Being
                                        Sealed and Locked
                                                                   _CL
                                                                                      1'Min.
                                       Tank Spacing and Fill in Accordance
                                     With Tank Manufacturer Specifications
                                                                      Slot Size 0.020"
                                                Groundwater
            t
           5' Min.
Observation Wells: Each Well is 2" Min. Dia. PVC Pipe
Slotted From 2' Below Ground Surface to Bottom.
Wells Inside Excavation Are Installed to Bottom of Excavation.
Wells Outside Excavation Are Installed Either 5' Into Groundwater or
2 Feet Below Bottom of Tank, Whichever is Deeper.
V
                                            Figure  1-2
                           Example  of Observation  Well  Installation10
                                                   1-5

-------
Backfill




'N

A

A


•^ 	 Manwa
A n A





                                                                            Perforated
                                                                           •  PVC
           Water Table
CAP
                                     Figure 1-3
                          Example of Vapor Monitoring Well
                                        1-6

-------
                                         SECTION 2
                        Conclusions  and Summary of Results
2.1  Conclusions

Response to the vendor survey  accounted for
approximately 71 percent of the identified vendors.
The response was almost universal from vendors of
equipment marketed specifically for LIST applications.
The literature search conducted in 1986 as part of this
study clearly demonstrated a lack of useful, published
information regarding external  (out-of-tank) petroleum
leak monitoring  devices and a need for the current
program to be performed.  Although much valuable
information was gained from this study, additional
work will be necessary before  performance standards
and certification procedures  can be developed for
each category of leak monitoring techniques.

Vendor responses to the questionnaire provided a
basis for dividing the petroleum leak monitoring
techniques Into  four basic categories: intermittent
liquid-phase detection, intermittent gas-phase
detection, continuous liquid-phase detection, and
continuous  gas-phase  detection.   Sufficient
information was  received from the vendor survey to
assess and compare the performances of the four
general types of  techniques and,  to a lesser extent, to
compare one technique  with another. However,
insufficient data exist to adequately compare the
product of one  vendor with the  product of  another
vendor when both are based on the same principle of
operation.   Also, the  vendor responses  were
inadequate in two important areas: (1) description of
common  interferences  and  operational  or
maintenance  problems  and  (2)  provision of
certification procedures.

Caution should be observed when evaluating monitor
performance based solely on vendor-supplied data.
Additional data  based on independent third-party
evaluations and on the operating experience of actual
users is  needed to  support the development of
performance specifications for out-of-tank leak
detection monitors.

2.2  Summary of Results

A summary of the results of this investigation is
provided below.
2.2.1   Summary of General Findings for
       External Leak Monitoring Systems

All of the external leak monitoring systems  for
petroleum hydrocarbons shared some  design
requirements, detection limitations,  installation
options,  and maintenance claims, according to
vendors.  The external leak detection devices usually
require monitoring  wells  or boreholes  placed
downgradient in the excavation pit.  The devices are
all designed for use with hydrocarbon  products,
though they may work with other materials. They can
all be retrofitted at  existing installations.   Finally, all
vendors state that low or no maintenance costs are
typically incurred.

2.2.2   Summary of Findings for Intermittent
       Liquid-Phase Detector

Intermittent liquid-phase  petroleum leak detectors for
USTs are inexpensive ($10 to $100) and simple to
operate.  They are currently marketed and are widely
used.  They can neither detect vapors nor provide
nonspecific detection of liquid hydrocarbons.  The
vendors  list no potential interferences; therefore
(based on vendor information alone), the potential for
false readings is  low.  The  devices respond to
approximately 1/32 to  1/64 inch of product.  The
usable life for these  types of sensors varies from
necessary replacement upon detection to indefinite.

2.2.3   Summary of Findings for Continuous
       Liquid-Phase Detectors

Continuous liquid-phase  petroleum leak detectors for
USTs have been on the market for up to 15 years, and
some vendors have thousands of devices in current
use.   Costs range  from $400 to $1,500 for control
panels and from $100 to $700 for sensors.  Estimates
for installation costs vary widely.  Product-soluble leak
detection  devices will respond to both liquid and
vapors. Most continuous liquid sensors respond to 1/8
to 1/32 inch of liquid within 0 to 10 hours (once liquid
comes in contact with the sensor).  Some potential
interferences include  hydrocarbons, ultraviolet (UV)
light, water vapor, ice, and reduced sulfur compounds.
False positive readings may be caused by these
interferents and,  in some models, by algae or
                                               2-1

-------
mechanical failure.  The control boxes can usually
accommodate multiple sensors and  have a long
service life.

2.2.4   Summary of Findings for Intermittent
       Gas-Phase Detectors

Intermittent gas-phase  petroleum hydrocarbon leak
detectors for USTs have been commercially available
for up to 10 years, and some vendors have hundreds
to thousands in current  use (not necessarily for UST
systems).  Costs range  from $100 to $1,700  for
sensors.  Estimates for  installation costs vary widely.
Some gas-phase leak detectors (e.g.,  GC's) give a
compound-specific response.  Detection limits range
from low part per billion  (ppb) to 1,500 part per million
(ppm) for the  lower limit  up to 10 percent to 100
percent of the lower explosive limit (LEL) for the upper
limit.  Response time is normally within seconds.  A
number of gas species may act as interferents, and
both false positive and false negative readings  are
possible.   The control panels have a long service  life,
but generally they can accommodate only one sensor.
These types  of detectors may involve appreciable
labor costs and may require special maintenance.

2.2.5  Summary of Findings for Continuous
       Gas-Phase Detectors

Continuous gas-phase petroleum hydrocarbon leak
detectors are generally  new to the  underground
storage tank market, and few are  in current use.
However, thousands of  these types of detectors have
been in use for up to 20  years in other applications.
Costs range from $500 to $5,000 for control panels
and from $65 to $1,500 for sensors. Installation costs
vary widely.  Certain devices within this category give
compound-specific responses.  Detection limits range
from 10 to 100 ppm at the lower end up  to 100 percent
of the lower explosive  limit (LEL). Response time is
very rapid. A relatively large number of interferences
were given, and both false positive and false negative
readings are possible.  The control boxes can usually
accommodate multiple sensors and have a long
service life. Sensor life ranges from 1 to 10 years.
                                                 2-2

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                                          SECTION 3
                                    Technical Approach
The technical approach to this project consisted of a
literature search, compilation of a vendor list, a vendor
survey, and evaluation of the data collected from this
survey. Each of these tasks is described below.

3.1  Literature Search

A literature  search was performed  to identify and
obtain published documents relating to the UST field
in general and to out-of-tank leak monitoring methods
in particular.  In addition, several researchers active in
the area were asked for status reports of their current
projects, and product literature was solicited from
vendors.    Only limited  information  regarding
commercially available leak monitoring systems was
obtained from the literature; this information is listed in
the bibliography in Section 6.

3.2  Vendor List

A vendor list was generated  to facilitate the vendor
survey (see  Appendix A).  The list, based on vendor
information obtained from the open literature and from
other researchers, was  augmented  by information
from other Radian projects, the Project Officer, and
telephone inquiries.  Each  vendor was called to
ascertain what product(s) are  currently marketed for
UST applications and to obtain product literature.
3.3  Vendor Survey

A vendor survey was performed to  gather specific
information regarding performance data for each type
of out-of-tank sensing device currently in use. The
specific types of performance information requested
included specificity, threshold  detection, response
time,  interferences,  drift,  precision,   noise,
recommended operating environment,  and service life.
These terms, defined in the glossary, are important
because they are the major categories by which
system performance can be evaluated.  Other data,
including capital cost,  recommended  installation and
operation procedures,  and maintenance costs, were
also  obtained from the vendor  survey.  These data
were used to develop generic performance categories
for each leak detection classification group(s) and
performance ranges for each performance category.
The questionnaire format can be  found in Appendix B.
                                                 3-1

-------

-------
                                          SECTION 4
                                            Results
This section presents and discusses the results of the
vendor survey.  Section 4.1 gives general information
regarding the survey. Vendor responses to the survey
are tabulated in Section 4.2, and summary tables and
tables listing  the  responses  of each  vendor are
presented.  The leak monitoring devices are evaluated
in Section 4.3, and the results are discussed in
Section 4.4.

4.1   Discussion of Survey

Table 4-1  shows the vendor list generated for this
project.  The  leak monitoring systems listed include
both systems designed and marketed specifically for
UST applications and general  analytical  equipment.
The list is as complete as possible, though it is
probable  that additional vendors exist.   Only
commercially available leak monitoring  techniques
were considered in this study.  Appendix A lists the
mailing address, telephone  number, and technical
representative for each vendor.  Vendors identified
since the  survey was completed  are  included  in
Appendix A, but not in Table 4-1.  Each vendor was
called to  determine which products were being
marketed  or  would  be most suitable for UST
applications. A questionnaire was sent in early 1986
to each vendor, except for  vendors of grab sampling
equipment, chemical-sensitive  pastes, and detector
tubes.  These types of monitoring devices were
thought to  be sufficiently simple  so that no information
other than that contained in the  product literature was
deemed necessary.  As can be seen in Table 4-1,
vendors who  market products  in several categories
sometimes completed questionnaires for only one
product, implying  that this  was the product they
emphasized in their marketing.  Also, it should be
noted that  two  vendors chose not to participate in the
survey and that several other companies  did not
submit responses.

A total of 49 vendors offering a total of  69 products
related to leak monitoring for UST systems were
identified.  Product  literature was received for 63 (91
percent) of the products.   Survey forms were
completed  and returned by  30 of the 42 (71 percent)
vendors queried. Survey forms were completed and
returned for 44 of the  62 (71 percent) products
covered by the  survey.  Survey forms were also
received from three vendors of interstitial monitors:
 Raychem, Emco Wheaton, and Perma-Pipe.  Their
 devices respond  to  the presence of petroleum
 hydrocarbons as opposed to interstitial monitors that
 detect pressure or liquid-level changes.  They are,
 therefore, very similar  to external monitoring devices
 (and, as noted earlier, some external monitoring
 devices are  suitable for use as interstitial monitors).
 However, these devices fall outside the scope of this
 project, and therefore, these survey responses are not
 included in this compilation.  A second device offered
 by Emco Wheaton  is suitable for external monitoring
 and is included in the study.

 The  EPA Office of Underground Storage Tanks
 (OUST) has  compiled a list of leak detection methods
 and manufacturers that contains over 250 products.
 The OUST list  includes the vendors and products
 identified in  this document,  as  well as integrity test,
 inventory control, line detector, and annular space
 monitoring methods that are outside the scope of this
 study.

 4.2  Tabulated Results From Survey

 This  section describes the  principle  of  operation of
 each leak monitoring technique and is followed by a
 series of tables summarizing the vendor responses to
 the questionnaire.

 4.2.1   Principle of Operation

 The principle of operation for each leak monitoring
 device listed in Table  4-1 is discussed  below.  The
 discussion of the principles of  operation has been
 published previously7.  The devices fall into four
 categories according to whether they  detect gases or
 liquids, intermittently or continuously,  as depicted in
 Table 4-2.

 The sampling approach required varies among the
 four categories  of leak monitoring devices.  Liquid-
 phase techniques require  a  monitoring well screened
 at the surface of the groundwater table or connected
 to a collection sump.   Continuous  liquid-phase
 techniques use some type of sensor installed in the
 monitoring well to  monitor the liquid-air interface.
 Intermittent  liquid-phase  techniques  involve either
temporarily placing a sensor in the  monitoring well or
 removing an  aliquot of  the well water with a bailer or
                                               4-1

-------
Type of Detector/
Company
Intermittent Liquid-Phase
Chemical-Sensitive Paste
Kolor Kut Products
McCabe
Grab Samplers
NEPCCO
Norton
Continuous Liquid-Phase
Interface Probe
Comar, Inc.
EMTEK, Inc.
Marine Moisture Control
Oil Recovery Systems, Inc.
Product-Soluble Devices
EMTEK, Inc.
IFP Enterprise
In-Situ, Inc.
K&E Associates
Pump Engineer Assoc.
Technology 2,000, Inc.
Electrical Resistivity Sensors
Total Containment
Thermal Conductivity Devices
Leak-X
Oil Recovery
Systems, Inc.
Pollulert Systems (Mallory)
Universal Sensors
and Devices, Inc.
Table 4-1
List of Vendors and Response to Survey
Literature Survey
Device Name/Model Number Received Received Comments
Water & Gasoline Finding Pastes
Water & Gasoline Indicator Pastes
Liquid Samplers3 and Bailers
Bailers3
Model 807 Tank Monitor
Model 808 Tank Monitor
Model 809 Tank Monitor
PLD-17 Pipeline Monitor
Electronic Well Gauging3 Light (EWGL-12)
Sonic Ullage Interface3 Probe
Interface Probe'3
Detect ran
Oil Fuse
Petrochemical Release Monitor
PMS-800
Sentinel
TOLTECH Hydrocarbon Monitor
Total Containment Cable-TC3000
Leak-X System
CMS Variable Level System
FD102andFD103
Leak Alert System
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
—
X
X
n/a
n/a
n/a
n/a
X
X
X
X
~
-
X
"
X
X
«
X
X
X
—
X
X
4-2

-------
Table 4-1
List of Vendors and Response to Survey (continued)
Type of Detector/ Literature Survey
Company Device Name/Model Number Received Received Comments
Intermittent Gas-Phase
Combustible Gas Detectors
MSA
Detector Tubes
MSA
National Draeger, Inc.
FIDs
Foxboro Analytical
Portable GCs
AID, Inc.
HNU
Microsensor
Technology Inc.
Photovac, Inc.
Sentex Sensing Tech., Inc.
XON Tech
Infrared
Foxboro Analytical
Horiba Engineering
PIDs
AID, Inc.
Astro Resources
HNU
Photovac, Inc.
Continuous Gas-Phase
Catalvtic Sensor Devices
Bacharach Instrument Co.

Gas Tech, Inc.
"* " ~ "* "^ «^— •—
Several models3
Samplair Pump & Test Kit3
Gas & Vapor3 Detection Products

Century OVA3
Model 5903
Models 201, 301 D, 501 a
Michromonitor3
Photovac 10A103
Scentor3
GC-8103

Miran3
IR Hydrocarbon3 Gas Analyzer

Model 580a
Trace Gas Analyzer-1 01 03
Model P1 1 01 3
TIP3
Underground Tank Monitor
TLV Sniffer3
Model 303a
Model H Gaspointer3
Model 12383
^^"""^^^^•^ """^^"""•••^^^••••^^••••••^^••••"••^••••••••••^••B
X
X
X

X
X
X
X
X
X

~
X

X
X
X
X
X
X
X
X
X
n/a
n/a

X
X
•<•
X
»
X

~
X

X
X
X
X
X
X
X
X
-
4-3

-------
Table 4-1
List of Vendors and Response to Survey (continued)
Type of Detector/
Company Device Name/Model Number
Industrial Scientific Devices LD-2223
Intek Corp. IGD
Lumidor Safety Products Model CRP-1
Rexnord Gas Detection Combustible Gasa Detection System
Products
Diffusion Sensors
Adsistor Technology Adsistor Sensor3
Emco Wheaton Leak Sensor II Vapor Probe
EMMCO Enterprises Env. Control Safety Monitoring System
Spearhead Tech., Inc. STI 2X12 Inground Tank Monitor
Metal Oxide Semiconductors
Armstrong Monitoring 4200 Sensor
Azonic Technology Corp. Enviro-Ranger
Calibrated Instrument, Inc. Pure Air Monitor
Enmet Corp. Several models3
Genelco, Inc. Soil Sentry
Harco Corp. Multi Ram 12
International AG5000 & AG51 00a
MSA Tankgard
Oil Recovery Systems, Vapor CMSb
Inc.
Universal Sensors Leak Alert
and Devices, Inc.
U.S. Industrial Products Co. Tank Monitor
Product-Permeable Devices
Teledyne Geotech LASP System
W.L Gore LEAKLEARN
Literature
Received
X
X
X
X
X
X
X
X
X
X
X
X
X
-
X
X
"-
X
X
X
X
Survey
Received
X
X
~
X
X
X
X
X
X
X
X
X
X
-
-
X
"
X
X
X

Comments


Vendor will
not respond
to survey















Vendor will
not respond
to survey
3 Not marketed specifically for UST applications.
b Not known if product marketed specifically for UST applications.
4-4

-------
pump.  Monitoring devices that collect pore liquids
(e.g., suction cup lysimeters) in the vadose zone are
being examined by another member of the EPA-EMSL
project team.  These devices are currently marketed
commercially  but not to routinely monitor leaks or
spills from underground storage tanks.  Gas-phase
monitoring  techniques--both  continuous  and
intermittent-generally involve some type of extractive
pump and sensor.  The sample  is drawn from the
headspace of a monitoring well or from some type of
soil probe and is moved to a control box containing the
sensing element. However, in some of the continuous
gas-phase techniques, the sensing element may be
below ground,  and  an  extractive pump is  not
necessary, though  its use will increase the vapor
transport rate and will shorten the detection time.

Principle of Operation - Intermittent Liquid-Phase
Detection Techniques

Chemical-sensitive pastes.  Separate pastes that
change color in the presence of liquid water and
hydrocarbons (gasoline  or  oil)  are available for
sampling observation wells  or tank  contents.  The
                    Table 4-2
          Commercially Available Leak
             Monitoring Techniques
   Monitoring
   Category3    Technique
   Intermittent   1. Chemical-sensitive pastes
   Liquid-Phase  2. Grab sampling

   Intermittent   1. Combustible gas detector
   Gas-Phase   2. Detector tube
               3. Flame-ionization detector
               4. Portable gas chromatograph
               5. Infrared detector
               6. Photoionization detector

   Continuous   1. Interface probe
   Liquid-Phase  2. Product soluble device (includes
                  electrical resistivity detectors)
               3. Thermal conductivity device

   Continuous   1. Catalytic sensor
   Gas-Phase   2. Diffusion sensor
               3. Metal-oxide semiconductor
               4.  Product permeable device
  aTypical use of technique. There is some overlap
  between intermittent and continuous techniques.
paste(s)  is spread in a thin layer along  a weighted
tape measure.  The tape measure is lowered into the
well or tank until the bottom is reached.  The tape is
retrieved, and the level of the various liquid layers
present is read directly from the tape.

Grab  sampling.  Grab  sampling of liquid  samples is
usually performed by using a bailer,  i.e., a Teflon,
plastic, or stainless steel pipe with a ball valve in the
bottom, as in Figure 4-1. The thickness of any product
layer  is determined  visually, and  samples  may be
decanted for more detailed analysis as required.

Principle of Operation -  Intermittent Gas-Phase
Detection Techniques

Combustible gas detectors.   In combustible gas
detectors, a sample  gas-air mixture comes in contact
with a heated, catalytic filament.  The burning sample
gas raises  the temperature of the detector and,
consequently, results in a corresponding  increase in
electrical resistance.  The change  in  electrical
resistance is proportional to concentration  and can be
measured with a Wheatstone  bridge or equivalent
                                                                                 Lifting
                                                                                 Line
                /\
                             Clear Acrylic
                             Bailer with
                             Graduations
                             On Side
                             Check Ball
                   Figure 4-1
         Bailer Used for Grab Sampling
                                                4-5

-------
                                   Principle of Operation
                                       Beam Trimmer


                                       Reference Cell
                                 Preamplifier
Control Unit
 Amplifier
                            Figure 4-2
         Schematic of an Infrared Radiation (IR) Detector9
Collector Electrode
                                             Compression Spring
                                             Lamp Housing

                                             Lamp


                                             High Voltage Contact
                                              Lamp Window
                                              lonization Chamber
                                              Detector Exit
                                                  Bias Voltage
                                Sample Inlet
                             Figure 4-3
          Schematic of a Photolonization Detector (P1D)10
                                4-6

-------
electronic circuit.  Combustible gas detectors are not
sensitive to low levels of hydrocarbon vapors and are
susceptible to catalyst poisoning from lead or other
interferents.

Detector tubes. The headspace of observation wells
can be monitored by using detector tubes.  The
sample is collected via a hand-operated bellows pump
or an automated battery-powered pump. The sample
gas passes through replaceable glass tubes filled with
an  inert support  that has been impregnated  with
chemicals designed to produce a  colorimetric
indication in the presence of selected gases, vapors,
or aerosols.   Detector tubes for a variety of gas
species and measurement ranges are available.

Flame-ionization  detectors.   The flame-ionization
detector (FID) operates on the  principle that most
organic compounds are  pyrolyzed when introduced
into a hydrogen-oxygen flame and that ions are
produced as part of the process. A charged electrode
collects the  ions, and  the  resulting current is
measured. FIDs show good response to methane and
other aliphatic compounds.

Portable gas chromatographs.  In gas chromatography
(GC), sample gas is transported by a carrier gas over
       Compressed Air
          Cylinder
                                     Alarm Relay
                                      Pressure
                                     Drop Sensor
 a  stationary solid- or  liquid-phase material.  The
 sample is  chromatographically separated into its
 various  components, and each compound  is
 sequentially detected at one or  more gas detectors.
 GC permits  both  monitoring for the presence  of
 hydrocarbon species and identification of the
 hydrocarbons present.  Several of the available
 portable field GCs require no external support
 equipment  such as compressed gas cylinders, AC
 power, integrator, etc.  Sample collection can be
 accomplished by using gas-tight syringes,  sorbent
 cartridges,  evacuated  stainless steel canisters, or
 polymer gas bags.'  Most GCs require injection of sub-
 mL sample  volumes and do not contain an extractive
 pump for continuous sample monitoring.

 Infrared detectors.   Infrared radiation (IR) detectors
 are based on the absorption of infrared radiation by
 covalent bonds that result in  increased vibrational or
 rotational energy in the gas molecule.  A typical
 instrument contains  an  IR lamp source, sample and
 reference cells, filters, and  an infrared light-sensitive
 detector, shown in Figure 4-2. The light is split and
 passes through both bells  simultaneously.  Any
difference in power between the  two  outlet beams  is
due to absorbance by the sample and is sensed by
the detectors and read out as concentration.  The
                                                    Air Line
                               Ground
                               Surface
                                                                                  Groundwater
                                                                                  Level


                                                                                  SBC Walled
                                                                                  Tube
                                                                Monitor Well
                                           Figure 4-4
                            Schematic of Leak Monitoring System Using
                                Product-Soluble Pressurized Tube7
                                               4-7

-------
wavelength of light or the path length of the sample
cell can be varied according to the species  being
monitored and to change the sensitivity.

Photoionization detectors.  The photoionization
detector (PID) uses a high energy ultraviolet lamp to
ionize the sample  drawn into the instrument via an
internal pump.  A typical schematic is shown in Figure
4-3. The ionized  sample produces an ion current
proportional to concentration which is measured with
an  ammeter.  The  PID  is  not  sensitive to any
compound having an  ionization potential greater than
the photon energy from the light source.  Insensitive
compounds include methane, ethane, and the major
atmospheric constituents.

Principle of Operation - Continuous Liquid-Phase
Detection Techniques

Interface probes.  Interface probes use a combination
of an optical sensor and a thermal conductivity sensor.
The optical sensor works via a pulsed beam of
infrared light being directed down a probe shaft.  If the
prism-shaped probe  tip is dry, the  light is reflected
back up a second shaft where it is detected by a
phototransistor. If  the probe tip is immersed in liquid,
the  light is refracted  into  the  liquid and therefore
interrupts the signal  to.the monitor. A conductivity
sensor  is used to determine if any liquid present  is
polar or nonpolar.

 Product soluble devices. Product soluble devices use
 a styrene-butadiene  copolymer (SBC)  soluble  in
 gasoline but riot in water.  This principle can be used
 in a number of ways to  detect leaks.  One method is to
 construct  SBC  hoses and suspend them in a
 monitoring well, shown in Figure 4-4. The hose is kept
 pressurized, and the system pressure is monitored.
 Any product that encounters the hose will dissolve it
 and will create an air leak.  The sensitivity of the
 detector, which can be varied, depends  on product
 type, hose thickness, and operating pressure.

 Several products are marketed wherein dissolution of
 an  SBC component activates a mechanical  or
 electrical alarm, illustrated in Figures 4-5 and 4-6.  In
 an  electrical resistivity sensor, a monitor circuit
 continuously reads a  resistor at  the end of a SBC-
 coated conductive cable.   The cable contains two
 conductor wires, as in Figure 4-7.,  Degradation of the
 SBC coating permits the two wires to touch, and the
 touching causes a decrease in resistance.  Another
 example of an SBC-based system is one that uses a
 SBC resin cord connected to a spring-loaded indicator
 that is weighted down  and placed in a monitoring well.
 Dissolution of the  SBC causes the weight to  be
 released  and the indicator  device to  rise  and to
 activate an alarm.
Thermal conductivity devices.  Thermal conductivity
sensors are used for continuous monitoring of liquids.
The sensor floats on the liquid surface in a monitoring
well, shown in Figure 4-8.  A heating element in the
float is periodically activated,  and the heat loss is
monitored. The differences in heat loss vary between
water (polar) and hydrocarbon (non-polar) compounds
and are detected. The sensor transmits a signal to a
control box to activate a visual or audible alarm when
non-polar liquids are detected.  Thermal conductivity
devices have been widely used. Typical maintenance
problems include (1) biological growth on the probe
that  insulates  it and (2) problems with ice or other
obstructions that prevent the sensor from riding on the
liquid surface.

Principle of Operation - Continuous Gas-Phase
Detection Techniques

Catalytic sensors. Catalytic sensors are a refinement
of the combustible  gas  detectors described earlier.
They contain a second heated  element that has been
coated to be non-reactive with hydrocarbon gases and
that acts as a reference cell.

Diffusion  sensors.  Diffusion sensors (commonly
referred to as  adsistors)  are  similar in principle to the
MOS detectors described below.  Gaseous diffusion
carries sample gases into contact with the adsorptive
material in  the sensor; this process changes the
resistance of the sensor. No heating element is used.
The sensor detects  any gas with  a Van der Waals "a"
constant (a  measure of the  attractive force between
molecules)  above  a certain threshold value.  The
major atmospheric gases are not  detected and are not
interferents.

 Metal-oxide semiconductors.  Metal-oxide semi-
 conductors (MOS) represent  one method used for
 continuous,  gas-phase leak monitoring.  A heater and
 collector are embedded in a solid-state cell which  is
 composed of metal and non-metal oxides of transition
 elements.  At operating temperature, a specific
 resistance exists between the  sensor elements. Gas
 molecules are dissociated  into  charged ions or ion
 complexes on the surface  of the sensor.  The
 resistance of the element  junction changes  in
 proportion to the concentration of  certain gas
 molecules.  Either the sensor is placed in  the
 monitoring well, or a sample  is  aspirated to the sensor.
 The latter configuration allows one sensor to monitor
 several locations.

 Product permeable devices.  Several materials are
 available  that  are permeable to hydrocarbons
 (oleophilic)  but not to water (hydrophobic).  The best
 known of these materials  is  Gore-Tex°.   Two leak
 monitoring  systems use these selectively permeable
                                                  4-8

-------
                              Spring Loaded Indicator


                               Ground Surface
             Figure 4-5
Schematic of Mechanically Activated,
      Product-Soluble Device7
                4-9

-------
Ground Surface
                                    Spring Loaded
                                      NC Switch
                              Figure 4-6
                  Schematic of Electrically Activated,
                        Product-Soluble Device7
                                  4-10

-------
To Control
  Box or
 Next Well
                                                                    100 Q
                                                                  Wire Wound
                                                                    Resistor
                                                                Ground Surface
                                  Figure 4-7
               Schematic of Electrical Resistivity Sensor Coated
                        With Product-Soluble Polymer?
                                     4-11

-------
membranes.  In one, the membrane  surrounds
perforated tubing, shown in Figure 4-9.   Gases that
diffuse into the tubing are  pumped to a metal-oxide
semiconductor detector (discussed above). The time
delay between  initiation  of the pump cycle and
detection indicates the location of the leak.  In the
second system, the membrane surrounds a coaxial
cable.  Oil diffusion through the membrane causes
capacitance changes in the cable and indicates the
presence of a leak.  Pulse reflection techniques are
used to locate the position of the leak along the cable.

4.2.2   Other Results

Tables 4-3 through 4-7 summarize the information
provided by vendors.  The tables address detection
specificity, detection capability,  experience, cost, and
recommended procedures. Vendor  responses have
been  condensed to a typical response or operating
range per type  of  monitoring technique, and
information from the product literature and scientific
judgment  are also incorporated.  Responses from
each vendor are tabulated in Appendix C.

4.3   Evaluation of Results

The division of leak monitoring techniques into
performance categories, the cost-effectiveness of
those techniques, and method selection as a function
of site-specific factors are evaluated in this section.
The evaluation is by type  of monitoring  system.
Insufficient information exists at this  time to  evaluate
products within a given system type adequately.

4.3.1    Performance Categories of Leak
        Monitoring Techniques

One of the main objectives of this phase of the project
was to divide  the  large  number of commercially
available leak  monitoring products into groups of
—                                        to»uff*E
                                     MOH/WKM& WELL 5CXEEN
                                                . OK
                                   ZSTA/NLESS STEEL (MOT SUPPL/ED1
             (JfJLEEQKOUND MSTALLATIQN
             (TYP/C.AL &ASOLINE
                                              Figure 4-8
                   Schematic of Typical Installations of Thermal Conductivity Sensor11
                                                 4-12

-------
u
n^| total nimmng itmtr i _^— ^— — — —
Running time 1
Corresponds
to Location 1

	 *••»
Pump Small k Leakage
iL Switched On A Leakage Peak j\ Peak


End
L±!
                      Gas
                  Concentration
                                                               Figure 4-9
                                                 Schematic of Product-Soluble Device12

-------
Table 4-3
Detection Specificities of Various Leak Monitoring Techniques
Type of Detects
Detector Gas
Intermittent Liquid-Phase
Grab Samplers No
Chemical- No
Sensitive Paste
Continuous Liquid-Phase
Interface Probe No
Product Soluble Yes
Devices
Electrical Yes
Resistivity Sensors
Thermal Con- No
ductivity Devices
Intermittent Gas-Phase
Detector Tubes Yes
Combustible Yes
Gas Detectors
PID's Yes
Portable GC's Yes
FID's Yes
Infrared Yes
Continuous Gas-Phase
Catalytic Sensor Yes
Devices
Metal Oxide Semi- Yes
Conductors
Product Yes
Permeable Devices
Diffusion Senors Yes
Detects
Liquid

Yes
Yes

Yes
Yes
Yes
Yes

No
No
No
No
No
No

No
No
No
Yes
Type of
Compound
Detected

Immiscible
Liquids
Hydrocarbons

Hydrocarbons
Hydrocarbons
Hydrocarbons
Hydrocarbons

Variety of Gases
Hydrocarbons
Aromatics
Hydrocarbons
Aliphatics
Hydrocarbons

Hydrocarbons
Hydrocarbons
Hydrocarbons
Hydrocarbons
Detection
Adjustable
for
Specific
Compounds

No
No

No
Yes
No
No

Yes
No
No
Yes
No
Yes

No
No
No
Yes
aFalse positives that are due to background contamination from spills, etc.,
Potential
Interferents

None
None

None
Background HC's
UV Light
Background HC's
UV Light
ICE, H2S

None
Pb,H2O,O2,S
CO2,CH4,CI,etc.
Water Vapor
S cmpds.
None
Methane
Variable

Pb,H2O,O2,S
CO2,CH4,CI,etc.
CH4,H2O,CO,S
CH4,H20,S,
Background HC's
Gas
Displacement
False
Positives
or
Negatives3

Unlikely
Unlikely

No
N/A
No
Both

None
Both
Positives
No
Positives
Positives

Both
Both
Both
None
Severity
Interferents

N/A
N/A

N/A
Variable
Variable
Variable

Low
Potentially
High
Application
Dependent
N/A
Variable
Variable

Variable
Normally
Low
Variable
Unlikely
are possible with any of the detectors.
4-14

-------
Type of
Detector
Table 4-4
Detection Capabilities of Various Leak I
Detection Limit # of Sense
Lower Adjustable Upper Box
Monitoring Techn
rs
On-Line
Time
iques
Service Life
Control Box
Sensors
Intermittent Liquid-Phase
Grab Samplers
Chemical-
Sensitive Paste
1/32 in. No None N/A
1/64 in. No None N/A
N/A
N/A
N/A
N/A
Indefinite
N/A
Continuous Liquid-Phase
Interface Probe
Product Soluble
Devices
Electrical
Resistivity
Sensors
Thermal
Conductivity
Devices
1/8 in. No None 1-4
1/32 in. Yes None 4-15
1/32 in. Yes N/A 1
1/8 in. Yes N/A 10-15
Continuous
Continuous
Continuous
Continuous
>3 yrs.
>10yrs.
Indefinite
>3 yrs.
>5 yrs.
Til Leak
Detected
Indefinite
>2 yrs.
Intermittent Gas-Phase
Detector Tubes
Combustible
Gas Detectors
PID's
Portable GC's
FID'S
Infrared
0.5 ppm Yes 2000 ppm N/A
1500ppm No 100%LEL 1
0.1 ppm Yes 20,000 ppm 1-32
5 ppb Yes 2000 ppm 1
5 ppm No 1 0% 1
5 ppm Yes 100% 1
N/A
Continuous
N/A
N/A
N/A
N/A
N/A
10yr.
5-1 Oyr.
5-1 Oyr.
5-1 Oyr.
5-1 Oyr.
N/A
1yr.
2yr.
2yr.
Indefinite
Indefinite
Continuous Gas-Phase
Catalytic
Sensor
Devices
Metal Oxide
Semi-
conductors
Product
Permeable
Devices
Diffusion
Sensors
50 ppm No 100%LEL 1-8
10 ppm Yes 1% 1-32
10 ppm Yes 1% 1
100 ppm Yes 100% 4-16
Continuous
Continuous
Continuous
Continuous
lOyr.
10yr.
10yr.
10 yr.
>1 yr.
Syr.
Syr.
10yr.
4-15

-------
                                         Table 4-4
         Detection Capabilities of Various Leak Monitoring Techniques (continued)
Type of
Detector
Response
Time
Intermittent Liquid-Phase
Grab Samplers N/A
Chemical- <1 sec.
Lag
Time
N/A
N/A
Rise
Time
N/A
N/A
Fall
Time
N/A
N/A
Drift
N/A
N/A
Noise
N/A
N/A
Precision
N/A
N/A
Sensitive Paste

Continuous Liquid-Phase

Interface Probe  sec.-30 min.

               <20 min.
Product
Devices

Electrical
Resistivity
Sensors

Thermal
Conductivity
Devices
               1-10hr.
                  sec.
intermittent Gas-Phase

Detector Tubes  <1 min.

                Not Known
Combustible
Gas Detectors

PID's
               3 sec.
Portable GC's   Variable


FID's           10 sec.

Infrared         30 sec.

Continuous Gas-Phase

Catalytic        20 sec.
Sensor Devices
Metal Oxide
Semi-
conductors

Product
Permeable
Devices

Diffusion
Sensors
               <30 sec.
               <10 min.
               1 -5 sec.
Not Known   Not Known Not Known   Not Known  Not Known   Not Known

<20 min.    <1 min.     N/A         N/A         N/A         Not Known


MOhr.     <1 min.     N/A         N/A         N/A         Not Known



1-5 sec.     <1 sec.     <1 sec.      N/A         N/A         Not Known
Negl.       <1 min.      N/A        N/A        Not Known  Not Known

Not Known  Not Known   Not Known   Not Known  Not Known  Not Known
<1 sec.
N/A
<1 sec.
<1 sec.
3 sec.
N/A
10 sec.
30 sec.
5-1 0 sec.
N/A
10-1 5 sec.
30 sec.
                                                              <1%of     <1%of
                                                              Full Scale   Full Scale
                                                                                     10%
                                                              <1%of     <1%of     5-10%
                                                              Full Scale   Full Scale
                                                              Negl.
                                             Negl.
                                                              2%/day     <1%of
                                                              Full Scale   Full Scale
10%

<1%of
                                                                         1%of      5%
                                                                         Full Scale    Full Scale
2-3 sec.     17 sec.     20 sec.      2% of


3-10 sec.    20 sec.     30-60 sec.   Not Known  Negl.       1-10%
<10min.    20 sec.     30-60 sec.   Not Known  Not Known   Not Known
<1-5sec.   <1-5sec.    15sec-min.  Negl.
                                                                         Negl.
Not Known
                                            4-16

-------
Table 4-5
Experience of Various Leak Monitoring Techniques
Product Years
On On
Detector Market Market
Intermittent Liquid-Phase
Grab Yes Many
Samplers
Chemical- Yes Many
Sensitive
Paste
Continuous Liquid-Phase
Interface Yes 0.5
Probe
(cont. monitor)
Product Yes <1
Soluble
Devices
Electrical Yes 15
Resistivity
Sensors
Thermal Yes 1 0
Conductivity
Devices
Intermittent Gas-Phase
Detector Yes Not
Tubes Known
Combustible Yes Not
Gas Detectors Known
PID's Yes 2-10
Portable Yes 1-10
GC's
FID's Yes >5
Infrared Yes 10
Number
in
Service

1 ,000's
1 ,000's

12
>200
>500
1,000's

1,000's
Not
Known
>4.000
1,000's
Not
Known
100's
Has Leak
Been
Found?

Yes
Yes

No
Yes
Yes
Yes-
Many

Not
Known
Not
Known
Yes
Yes
Yes
Yes
Operating
Experience

Cheap &
Simple
Cheap &
Simple

Limited
Data
Not
Known
Not
Known
Used by
Some Major
Oils

Cheap and
Simple
Not
Known
Widely Used
as Portable
Instr.
Need Exper.
Operator
Widely Used
as Portable
Instr.
Not
Known
Maintenance
Problems

Minimal
Error
Minimal
Error

None
Ice
Minimal
Ice, Algae,
Hung-up
Float

Minimal
Poisoned
Catalyst
Calibration
Columns
Calibration
Not
Known
Cause
of False
Negatives

Operator
Operator

Break in
Cable
N/A
None
Elec. Short

Unlikely
Low
Sensitivity
Water
Vapor
Unlikely
Unlikely
N/A
Cause
of False
Positives

N/A
N/A

N/A
Bkgrnd. HC's
Polymer
Degrad.
Bkgrnd. HC's
Polymer
Degrad.
Fouled or
Hung-up
Probe

Gas Inter-
ferents
Not
Known
Gas Inter-
ferents
Unlikely
Methane
Gas Inter-
ferents
4-17

-------
                                             Table 4-5
                  Experience of Various Leak Monitoring Techniques (continued)
Detector
Product   Years     Number   Has Leak                             Cause      Cause
On       On       in        Been       Operating     Maintenance  of False    of False
Market   Market    Service   Found?     Experience    Problems     Negatives   Positives
Continuous Gas-Phase

Catalytic      Yes
Sensor
Devices

Metal Oxide   Yes
Semi-
conductors

Product       Yes
Permeable
Devices

Diffusion      Yes
Sensors
         1-15      >70,000   Yes
         0-12      >1,300    Yes
                            Yes
         1.5-20     >75,000   Yes
Used by      Poisoned
Some Major   Catalyst
Oils
             Not
             Known
            Not
           Known
Not
Known
Minimal
Water Vapor Unlikely
Elec. Short
Limited Use   Pump Burn-   Sensor     N/A
             Out          Break
Good
Minimal
None
Elec. Short
                                               4-18

-------
Table 4-6
Costs For Various Leak Monitoring Techniques
Capital Costs ($)
Type of Control
Detector Box
Intermittent Liquid-Phase
Grab Samplers N/A
Chemical- N/A
Sensitive Paste
Continuous Liquid-Phase
Interface Probe 1 ,200
(cont. monitor)
Product 400-1,200
Soluble Devices
Electrical 1 ,500
Resistivity
Sensors
Thermal 1,400
Conductivity
Devices
Intermittent Gas-Phase
Detector Tubes N/A
Combustible Not
Gas Detectors Known
PID's 3,900-6,300
Portable GC's 5,800-14,000
FID'S 5,000
Infrared 1,750-9,000

Continuous Gas-Phase
Catalytic 700-2,400
Sensor Devices (avg=1 ,000)
Metal Oxide 500-4,000
Semi- (avg=1 ,000)
Conductors
Product 5,000
Permeable
Devices
Diffusion 1 ,400-4,200
Sensors
Sensor

<100
<10


200

200-900

100-200


600-700



<100
Not
Known
200-1,700
N/A
N/A
N/A


65-200

28-1,500
(avg=100)

6/ft.


200-300

New
Facility

N/A
N/A


Not
Known
1,500-
11,000
2,800


2,500



N/A
Not
Known
N/A
N/A
N/A
1,750-
30,000

Not
Known
Not
Known

Not
Known

5,000

Installation Costs ($) (4 Tanks)
Old
Facility

N/A
N/A


Not
Known
3,000-
1 1 ,000
5,500


5,500



N/A
Not
Known
N/A
N/A
N/A
1,750-
30,000

Not
Known
Not
Known

Not
Known

7,000

Old Wei!

N/A
N/A


Not
Known
1 ,500-
7,000
3,300


4,200



N/A
Not
Known
N/A
N/A
N/A
Not
Known

Not
Known
Not
Known

Not
Known

5,000

Maintenance
Costs-$

Nil
Nil


Minimal

Minimal

Minimal


600/yr.



Nil
Not
Known
N/A
N/A
N/A
Variable


Minimal

Minimal


Minimal


0-1 ,800/yr.

Labor
Costs-$

High
Medium


Low

Low

Low


Low



Medium
Low

Medium
High
Medium
Medium


Low

Low


Low


Low


4-19

-------
Table 4-7
Recomended Procedures for Various Leak Monitoring Techniques
Can
Type of Are Wells System Be Recommend Utility Location
Detector Required? Retrofitted? Site Study Service to Tank
intermittent Liquid-Phase
Grab Samplers Yes
Chemical- Yes
Sensitive Paste
Continous Liquid-Phase
Interface Probe Yes
(cont. monitor)
Product Soluble Usually
Devices
Electrical Resist- Yes
ivity Sensors
Thermal Yes
Conductivity
Devices
Intermittent Gas-Phase
Detector Tubes Usually
Combustible Usually
Gas Detectors
PIDs Usually
Portable GCs Usually
FIDs Usually
Infrared Usually
Continuous Gas-Phase
Catalytic Sensor Usually
Devices
Metal-Oxide Usually
Semiconductors
Product No
Permeable
Devices
Diffusion Usually
Sensors

Yes
Yes

Yes
Yes
Yes
Yes

Yes
Yes
Yes
Yes
Yes
Yes

Yes
Yes
Yes
Yes

Yes
Yes

Yes
Yes
Yes
Yes

Yes
Yes
Yes
Yes
Yes
Yes

Yes
Yes
Yes
Yes

None
None

None
None or Elec.
AC Line
AC Line

None
AC Line
None or Elec.
None or Elec.
None
None or Elec.

None or Elec.
None or Elec.
AC Line
AC Line

Downgradient
Downgradient

Downgradient
Depends on
# of Sensors
In Excavation
Below Tank

Downgradient
Downgradient
Downgradient
Downgradient
Downgradient
Downgradient

Variable
In Excavation
In Excavation
Under Tank
Bottom
Distance
From Tank

In Excavation
In Excavation

On Perimeter
of Excavation
Variable
2ft.
2ft.
Bottom

In Excavation
In Excavation
In Excavation
In Excavation
In Excavation
In Excavation

Variable
1ft.
Not Known
Close
Proximity
\
4-20

-------
Table 4-7
Recommended Procedures for Various Leak Monitoring Techniques (Continued)
Number Adjustable
Type of of Sensors Calibration Instrument Use in Operating Temp.
Detector Per Tank Procedures Settings Wet Soil Environment Range
Voltage
Range
Intermittent Liquid-Phase
Grab Samplers
Chemical-
Sensitive Paste
N/A N/A
N/A N/A
N/A
N/A
Yes
Yes
N/A
N/A
>0°C
N/A
N/A
N/A
Continuous Liquid-Phase
Interface Probe
(cont. monitor)
Product
Soluble Devices
Electrical Resis-
tivity Sensors
Thermal
Conductivity
Devices
1 -4 None
1-4 None
4 None
4 None
None
None
None
None
Yes
Yes
Yes
Yes
Any
Any
Any
Any
-45-60°C
0-50°C
0-120°C
-40-50°C
N/A
85-1 35V
..
100-1 40V
Intermittent Gas-Phase
Detector Tubes
Combustible
Gas Detectors
PIDs
Portable GCs
FIDs
Infrared
N/A Cal. Gas
Not Not
Known Known
1-6 Cal. Gas
1 or More Cal. Gas
Not Known Cal. Gas
Not Known Cal. Gas
Yes
Not
Known
Several
Several
None
Zero/Span
Yes
Not
Known
Yes
Yes
Yes
Yes
N/A
Not
Known
Any
Non-
Explosive
Any
Any
N/A
Not
Known
0-50°C
0-50°C
0-60°C
0-40°C
N/A
Not
Known
11 0-1 20V
110-1 15V
N/A
11 0-1 30V
Continuous Gas-Phase
Catalytic Sensor
Devices
Metal-Oxide
Semiconductors
Variable Cal. Gas
1-2 Cal. Gas
Product 2 Cal. Gas
Permeable Devices
Diffusion
Sensors
1 or More Cal. Gas
None-
Several
None-
Several
Gain/Zero
Several
Yes
Yes
Yes
Yes
Any
Non-
Explosive
Any
Air
-20-50°C
-10->60°C
Not
Known
-75-70°C
105-1 30V
105-1 25V
Not
Known
105-1 25V
4-21

-------
Table 4-7
Recommended Procedures for Various Leak Monitoring Techniques (Continued)

Type of
Detector

Maint.
Require.

Maint.
Schedule

Calibration
Procedures

Calibration
Schedule


Flow Rate

Certifi-
cation
Surface
Vs. Under-
ground
Intermittent Liquid-Phase
Grab Samplers
Chemical-
Sensitive Paste
Cleaning
Cleaning

Before Use
Before Use

N/A
N/A

N/A
N/A

N/A
N/A

No
No

No
No

Continuous Liquid-Phase
Interface Probe
(cont. monitor)
Product
Soluble Devices
Electrical Resis-
tivity Sensors
Thermal
Conductivity
Devices
Inspect
System
Inspect
System
Inspect
System
Inspect
System

Once every
2yrs
2/yr.

Not Known

6/yr.


None

None

None

None


N/A

N/A

N/A

N/A


N/A

N/A

N/A

N/A


No

Yes

Yes

Yes


No
e
No

No

No


Intermittent Gas-Phase
Detector Tubes

Combustible
Gas Detectors
PIDs
Portable GCs
FIDs
Infrared

None

Inspect
System
Clean Lamp
Columns
Replace Fuel
Various

N/A

Not Known

As Needed
2/yr.
As Needed
Monthly

Std. Gas

Not Known

Zero/Span
Gas Stds.
Zero/Span
Gas Stds.

Continuous Gas-Phase
Catalytic Sensor
Devices
Metal-Oxide
Semiconductors
Product
Permeable
Devices
Diffusion
Sensors
Periodic
Calibration
Inspect
System
Not Known


Inspect
System
Variable

2/yr.

Not Known


4/yr.

Std. Gas

Std. Gas

Not Known


Electronic

As
Required
Not Known

Daily
Daily
Daily
Daily-
Monthly

Variable

Variable

Not Known


At Install.

Not Known

Not Known

0.05-0.6 L/min.
0.01 L/min.
Not Known
0.5-1. SL/mln.


0.5-1 L/min.

2 L/min.

0.7-1.1 L/min.


N/A

No

Not Known

Std. Gases
Std. Gases
Std. Gases
Std. Gases


Cert. Gas

Cal-Kits

Not Known


Not Known

No

No

No
No
No
No


No

No

No


No


4-22

-------
products with similar performance characteristics.
This grouping will make It easier to determine the
number of sets of performance specifications and
certification procedures that need to be developed in
subsequent phases of this project.

Analysis of vendor responses revealed that the leak
monitoring techniques fall into four relatively obvious
categories, illustrated in Figure 4-10. Several factors,
such as regulatory constraints and type of facility (old
versus new), proved to be unimportant at this time in
categorizing the techniques; this is contrary to initial
expectations.  There is some overlap between the
categories.  For instance, the product-soluble devices
will react  with  vapor  as well as liquid, though at a
much slower rate.

4.3.2  Site-Specific Factors

Table 4-8  summarizes the effect of site-specific factors
on the selection of a leak monitoring system.  In
general, the most important parameters affecting leak
monitoring systems are secondary containment and
groundwater depth.  If secondary containment is used,
the leak  monitoring system  can be simpler, and
continuous  monitoring is  less  important.  Deep
groundwater favors gas-phase detection  methods,
whereas  shallow groundwater favors liquid-phase
detection  methods.
                      4.4  Discussion of Results

                      This discussion of the questionnaire sections ranges
                      from general to specific comments.

                      4.4.1    Overall Results

                      As discussed earlier,  the leak monitoring techniques
                      fall into four categories:

                         o Intermittent liquid-phase detection;
                         o Intermittent gas-phase detection;
                         o Continuous liquid-phase detection; and
                         o Continuous gas-phase detection.

                       The techniques  within a category tended to have
                       similar capabilities and deficiencies.  The  relative
                       advantages and disadvantages of each technique are
                       summarized  in Table  4-9. In general, the intermittent
                       gas-  and liquid-phase monitoring techniques are not
                       only more labor intensive but also more reliable than
                       the automated,  continuous gas-  and liquid-phase
                       monitoring  techniques. Gas detection  is  more
                       sensitive than liquid  detection, but the equipment is
                       more complex and expensive and is more susceptible
                       to interferences.

                       The  survey response was better  than  expected in
                       terms of the  number of vendors returning completed
                                      All Leak Monitoring Techniques
                                                     O
                                 Automated/Frequent
                                      Sampling
                          Manual/Periodic
                             Sampling
              Continuous Monitoring Technique
                               Intermittent Monitoring Technique
                      High
Low
            High
Low
          Continuous,
          Gas-Phase
          Monitoring
          Technique
      Continuous,
      Liquid-Phase
      Monitoring
      Technique
Intermittent,
Gas-Phase
Monitoring
Technique
      Intermittent,
     Liquid-Phase
      Monitoring
      Technique
          1   Labor Requirements/Monitoring Duration
          2   Sensitivity/Equipment Complexity
                                              Figure 4-10
                                Decision Tree for Detector Classification
                                                  4-23

-------
                                       Table 4-8
                  Effect of Site-Specific Factors and Design Options on
                          Selection of Leak Detection Methods
 Variable
 Options
                                                Effect of Option on Leak Detection
 System Age
Tank Type
Secondary
Containment
Overfill
Protection
Groundwater
Depth
Excavation Type
Environmental
Considerations
 New installation

 Existing installation
Steel
Fiberglass
Coated steel

Double-walled tank
 Natural or synthetic liner



 Concrete vault



 Yes


 No



 Deep


 Shallow



 Highly variable

 Wet


 Dry
Environmentally-sensitive
area or very hazardous
product
None.

May be difficult to retrofit leak detection
capability.

None.
None.
None.

Monitor interstitial space.
Place leak detection equipment within
liner. Continuous monitoring not normally
necessary.

Place leak detection equipment within
vault. Continuous monitoring not normally
necessary.

None.
Vapor monitors may be unsuitable if
frequent spills result in high background
vapor concentrations.

Use U-tube type collection sump for new
installations.

Use one or more observation wells per
excavation.  Continuous monitoring
recommended.

Floating detectors may be unsuitable.

Liquid-sensing detectors preferable to
vapor-sensing detectors.

Vapor-sensing detectors preferable to
liquid-sensing detectors.

Continuous, vapor-sensing detectors
recommended.
                                         4-24

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                                              Table 4-9
               Relative Advantages/Disadvantages of Leak Monitoring Techniques
Monitoring
Category3/ Technique
                                Advantages
   Disadvantages
                             1  Simple, quick, and accurate
                             2  Inexpensive equipment
Intermittent Liquid-Phase

Chemical-sensitive paste




Intermittent Gas-Phase
Combustible Gas detector      1  Inexpensive gas-phase
                                analyzer
Detector tube
                             1  Inexpensive equipment
Flame-ionization detector,      1  Quick, accurate, and very
Portable gas chromotograph,      sensitive
Infrared detector, and
Photoionization detector
1  Does not provide continuous monitoring
2  Labor-intensive
3  Provides only limited information
   regarding nature of contamination
1  Insensitive gas-phase technique
2  Catalyst is subject to poisoning
3  Does not provide continuous monitoring
4  Labor-intensive

1  Does not provide continuous monitoring
2  Labor-intensive

1  Do not provide continuous monitoring
2  Labor-intensive
3  Expensive equipment
4  Experienced operator required
5  Not well suited for contaminated  areas
   or areas with high background
   concentrations
 Continuous Liquid-Phase

 Interface probe
                             1  Medium cost
 1   Subject to biofouling
 Product soluble device
 Thermal conductivity
 Continuous Gas-Phase

 Catalytic sensor, Diffusion
 sensor, and Metal-oxide
 semiconductor
 Product permeable device
                              1   Inexpensive equipment
                              2   Simple method

                              3   Detects vapor as well as
                                 liquid

                              1   Widely used method
                              2   Medium cost
                              1   Quick, accurate, and very
                                 sensitive
                              1   Can determine magnitude
                                 and location of leak
 1   Need to replace sensors every 6 months
 2  Device may degrade because of back-
    ground contamination, abrasion, or UV light
 1  Subject to biofouling
 2  Float mechanism may fail because
    of ice or physical obstruction
 1  Expensive equipment
 2  Not suitable for contaminated areas or
    areas with high backgound concentrations
 3  Catalytic sensor subject to catalyst poisoning

 1  Expensive equipment
 2  Little user experience to date
 3  Not suitable for contaminated areas or
    areas with high background concentrations
 4  Water may cause false alarm
 aTypical use of technique
                                                  4-25

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questionnaires; however, In some cases, the quality of
the responses was not acceptable.  Vendors were
particularly reluctant to discuss (or lacked data on)
maintenance problems  and false positive or negative
readings.  Also, in some cases, the description of
typical installed costs appeared inadequate.

4.4.2   Questionnaire  Results

Principle of Operation.  Many vendors were unclear
regarding the exact principle of  operation utilized by
their product.   Vendor literature was necessarily used
to augment the questionnaire responses.

Detection Specificity.  The majority of sensors respond
to vapor  or liquid; only diffusion sensors  and product-
permeable devices  respond  to both.  All  the
techniques respond  to most hydrocarbons  or
commonly stored petroleum products.  The sensors
cannot be adjusted to be  specific for a given product
(except for gas chromatographs).  However, some
sensors can be adjusted to increase their specificity to
a class of compounds.  For example, the dissolvable
component of  product-soluble devices  and electric
resistivity sensors can be of variable thickness to vary
the  sensitivity.  Similarly,  many gas-phase detectors
can be adjusted to increase their sensitivity to one
class  of  compounds over another.  A number of
potential interferents were  identified, and these appear
to be the major cause of false positive and false
negative results.   In  general,  the  impact  of
interferences on leak detectors is  not a major problem.

Detection  Capability.  As  expected, gas-phase
detection is much more sensitive than  liquid-phase
detection. The response time of all techniques Is less
than 1 minute except  for the product-soluble and
product-permeable sensors  which respond in less
than  20 minutes.   Drift,  noise,  precision, and
applicable test procedure information was very limited.
The majority of  the continuous techniques permit
multiple sensors to operate from  a single control box.
Finally, the estimated service life averaged 10 years
for control boxes and about 2 years for sensors.

Experience.  Thermal conductivity devices, grab
samplers, and  chemical-sensitive pastes are the only
techniques that have been widely used for monitoring
underground storage tanks.   The other techniques
either are new to the market or have been used in
other applications. Vendor responses regarding years
on the market  and  the  number of devices in service
are not  limited to use  of  the devices for UST
applications.   Information regarding operating
experience, maintenance problems, false negative
readings,   false   positive   readings,   and
repair/replacement experience was generally limited.
 Cost.  Costs for control box and sensors ranged from
 less than $100 to $14,000.  Gas-phase detection
 systems averaged about $4,000 versus $1,500 for
 liquid-phase detection systems. Installation costs may
 be as much as $30,000, but there were  limited
 responses to this question.  Most vendors thought
 maintenance costs were minimal.

 Recommended  Procedures.  In general, the  various
 leak monitoring systems require observation wells,
 can be retrofitted,  can operate under any soil
 conditions, should be  located within the tank
 excavation, and cannot differentiate  between spills
 and leaks.  Again, it should be emphasized that these
 conclusions are based only on the data provided by
 the manufacturers.  They gave only limited answers to
 maintenance, calibration, and certification questions.
 For calibration, the vendors typically responded either
 that none was  required or that some unspecified
 calibration gas or gasoline was needed.  Bacharach
 Instruments markets a calibration kit for their sensors.
 The general response to the question  on certification
was to use an unspecified gas standard.  However,
detailed certification procedures were given for two of
the leak monitoring devices: the electrical resistivity
 sensor produced by Total Containment and the
Adsistor sensor  marketed by several vendors.   In
addition, Rexnord states that their catalytic  sensor
device can be certified by "FM #6310-6330 procedure
and CSA #C22.2 No. 152  procedure."  Additional
testing procedure information had been solicited from
vendors and testing concerns.  Information collected
to date is summarized in Table 4-10 and will be used
 in designing test procedures during future work.

Vendors typically stated that their devices cannot
distinguish between  surface spills and  leaks.
 However, over time, all the leak monitoring  devices
 may be able to do so. Presumably, a surface spill will
 result in a "front" of contamination moving through the
soil with concentrations decreasing over time.  Those
devices that give a quantitative readout should show a
drop in concentration over time for a spill but not for a
 leak.   Devices that give a binary readout (alarm  or
 non-alarm) can be reset or can have the sensing
 element replaced  and eventually can distinguish
between spills and leaks.
                                               4-26

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                                        Table 4-10
                      Available Test Procedures and Results for Leak Monitors
Summary of
                           Testing Agency/
                           Vendor
                                        Test Information
                                                 In-house testing procedures and designs
                                                 (information not yet received).
                  Testing Agency


                  Testing Agency
1.  Active Leak Testing
                                                 Report for Adsistor ® (1970).  Tests consisted of:
2.  National Swedish
   Institute for Materials
   Testing
                                                         Boundary value for gasoline
3.  B.C. Research


4.  Bacharach


5.  C.S.A.


6.  Fire Marshall,
    Campbell, CA

7.  EMMCO

8.  Geneico
                  Testing Agency


                  Vendor


                  Testing Agency


                  Inspection Agency


                  Vendor/R&D

                  Vendor
 9.  Factory Mutual
     (P.M.)
                   Testing Agency
10.  In-Situ
                   Vendor
                                                         Relative humidity
                                                      3  Consumption
                                                      4  Tension
                                                      5  Temperature
                                                      6  Reaction time
                                                         Shock
                                                      8  Brine water
                                                      9  Self-sureness
                                                     10  Installation.

                                                 No additional testing data.
                                                 References were sent for further contacts.

                                                 P.M. and C.S.A. are contracted to test their detectors.
                                                 Contacts for both and P.M. reports were received.3

                                                 Test procedures pertaining to gasoline vapor
                                                 detectors (not yet received).

                                                 Monitoring  standards for Santa Clara and
                                                 inspection checklist were received.

                                                 Sensor operations information.

                                                 Soil cell designs, vapor sensor testing consisting of:

                                                       1   Frequency
                                                       2  Location
                                                       3  Calibration
                                                       4  Installation
                                                       5  Site Evaluation.

                                                  Approval standards for combustible gas detectors.
                                                  Discussed are the following:

                                                       1  Detector construction
                                                       2  Marketing (labeling)
                                                       3  Tests performed
                                                       4  Apparatus and test procedures

                                                  In-house testing procedures and specifications
                                                  along with draft test results. Testing considered
                                                  response time for liquid and vapor detection.
11. Pollulert Systems
12. Universal Sensors
and Devices, Inc.
Vendor
Vendor
In-house lab and field test results.
Soil cell tests for measuring diffusion rate.
    aF.M. reports are proprietary information
                                             4-27

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                                         SECTION 5
                                         References
1.  Jeyapalan, J. K., and J.B. Hutchison.
   Underground Storage Tanks-Leak Prevention,
   Leak Detection, and Design.

2.  Hazardous Waste Report-Trends & Analyses.
   The Next Regulatory Battle: Leaking
   Underground Storage Tanks, May 1984.

3.  Predpall, D. F., W. Rogers, and A. Lament. An
   Underground Tank Spill Prevention Program. In:
   Proceedings of Petroleum Hydrocarbons and
   Organic Chemicals in Ground Water, Houston,
   Texas, November 1984. pp.  17-32.

4.  Marketer's Report of the Texas Oil Marketers
   Association. Why Be Concerned about
   Underground Storage Tanks? June 1985.

5.  The Hazardous and Solid Waste Amendments of
   1984 to the Resource Conservation and Recovery
   Act, Subtitle 1, Sections 9001-9010 of U.S. Public
   Law 98-616, November 1984.

6.  Scheinfeld, R. A., and T. G. Schwendeman. The
   Monitoring of Underground Storage Tanks--
   Current Technology. In:  Proceedings of
   Petroleum Hydrocarbons and Organic Chemicals
   in Ground Water, Houston, Texas, November
   1985.
7.   Eklund, B. Evaluation of Methods for Leak
    Detection in Underground Storage Tanks and
    Connected Piping. In:  Proceedings of the Air
    Pollution Control Association's 79th Annual
    Meeting and Exhibition, Minneapolis, Minnesota,
    June 1986.

8.   Horiba Engineering IR Hydrocarbon Gas Analyzer
    Product Literature.

9.   HNU Model P1101 Product Literature.

10. Pollulert Systems FD102 Thermal Conductivity
    Sensor Product Literature.

11. Teledyne Geotech LASP System Product
    Literature.
                                               5-1

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                                        SECTION 6
                                       Bibliography
              This section contains a selected bibliography of general references and a listing
                         of other pertinent citations from the literature search.
6.1  Selected Bibliography

Leak Monitoring

American Petroleum Institute.  Observation Wells as
   Leak Monitoring Techniques.  Unpublished Draft
   Report, Washington, D.C. 1986.

Donaghey,  L. F.  Groundwater Protection through
   Early Detection of Hydrocarbon Leaks.  In:
   Proceedings of Oil Spill Prevention, Behavior,
   Control, and Cleanup Conference, Los Angeles,
   California, February 1985, Washington, D.C.,
   American Petroleum Institute, pp. 263-65.

Eklund,  A. G., and B. M. Eklund.  Integrity Test  and
   Leak Detection for Underground Storage Tanks.
   Edison Electric Institute. 1986.

Eklund,  B. Evaluation of Methods for Leak Detection in
   Underground Storage Tanks  and Connected
   Piping.  In:  Proceedings of the Air Pollution
   Control Association's 79th Annual Meeting  and
   Exhibition, Minneapolis, Minnesota. June 1986.

Lu, J.,  and W. Barcikowski.  Cost-Effectiveness
   Evaluation of Leak Detection and Monitoring
   Technologies for Leaking Underground Storage
   Tanks.   In:  Proceedings of the  National
   Conference on Hazardous Wastes and Hazardous
   Materials, Atlanta, Georgia. March 1986.

Petroleum Equipment  Institute. 1986 Petroleum
   Equipment Directory. PEL 1986.

Scheinfeld, R. A.,  J.  B.  Robertson, and T. G.
   Schwendeman.   Underground Storage Tank
   Monitoring:  Observation  Well  Based Systems.
   Ground Water Monitoring Review. Fall 1986.

The  New York State Department of Environmental
   Conservation.  Technology for the Storage of
   Hazardous Liquids. March 1985.

van Ee, J. J.  New Approaches to  the Evaluation of
   Leak Detection Monitors for Underground Storage
   Tanks.   In: Proceedings of the API/NWWA
   Petroleum Hydrocarbons and Organic Chemicals
   in Ground Water Conference, Houston,  Texas.
   November 1986.

Related Topics: Design, Installation, Operations,
Regulations, and Integrity Testing

American Petroleum Institute.  Installation  of
   Underground Petroleum Storage Systems. API
   Publication 1615. November 1979.

American Petroleum Institute. Recommended Practice
   for Bulk Liquid Stock Control at Retail Outlets. API
   Publication Number 1621. 1977.

American Petroleum Institute.  Recommended
   Practice for Underground Petroleum Product
   Storage Systems at Marketing and Distribution
   Facilities. API Publication  Number  1635.
   December 1984.

Anonymous.  EPA to Examine  Tank Leak Tests;
   Defines  Many  Causes  of "Noise." Petroleum
   Marketer.  September-October  1985.

Buonocore, A. 0., G. F. Kotas, and K. G. Garrahan.
   New Requirements for Underground Storage
   Tanks.   In:  Proceedings   of  the National
   Conference on Hazardous Wastes and Hazardous
   Materials, Atlanta, Georgia.  March 1986. pp. 246-
   250.

Curran, S. D.  Prevention and Detection of Leaks from
   Underground Gasoline  Storage Systems.   In:
   Proceedings of 6th National Ground-Water Quality
   Symposium, Atlanta, Georgia, September 1982.
   National Water Well Association, Worthington,
   Ohio. 1983. pp. 93-100.

Heckard, M.  States Crack  Down on Fuel Tank Regs.
   Fleet Owner, Small Fleet Edition.  March 1985.

Radian Corporation. State-of-the-Art Tank and Piping
   Technology and Installation  Practices.  Edison
   Electric Institute. 1986.
                                              6-1

-------
National Fire Protection Association, Inc. Underground
    Leakage of Flammable and Combustible Liquids.
    NFPA Document No. 329. June 1983.

New York  State  Department of Environmental
    Conservation.  Recommended  Practices for
    Underground Liquid Storage Systems. 1985.

New York  State  Department of Environmental
    Conservation.  Technology for the Storage of
    Hazardous Liquids. March 1985.

Niaki, S., and J. A. Broscious. Underground Tank
    Leak Detection Methods: A State-of-the-Art
    Review.   EPA  Contract No.  68-02-3069,
    EPA/HWERL-Cin. In Press.

PACE.  Underground Tank Systems: Review of State
    of the Art and Guidelines. PACE Report No. 82-3.

PACE.   Proceedings of Underground Tank Testing
    Symposium, Toronto, Ontario, May 1982.
    Petroleum Association for Conservation of the
    Canadian Environment.

Petroleum  Equipment Institute.  Recommended
    Practices for Installation of Underground Liquid
    Storage Systems. 1985.

Tusa, W. Underground Leaks: True Corporate Costs.
    Pollution Engineering.  February 1986.

U. S. Environmental Protection Agency.  More About
    Leaking  Underground  Storage  Tanks: A
    Background Booklet for the Chemical Advisory.
    EPA Office of  Toxic  Substances, Washington,
    D.C. October 1984.

Wilcox, H. K.,  J. D. Flora, C. L. Haile, M. J. Gabriel,
    and J. W. Maresca.  Development of a Tank Test
    Method for a National Survey of Underground
    Storage Tanks.   EPA-560/5-86-014, U.  S.
    Environmental Protection Agency. May 1986.

Woods,  P.  H., and D.  E. Webster.  Underground
    Storage Tanks:  Problems, Technology, and
    Trends,  Pollution Engineering 16(7):30-40,1984.

6.2  Additional  Citations Identified in
Literature Search

Adamowski, S. J., A. J.  Caracciolo III, and G. D.
    Knowles.    Underground Storage  System
    Assessment, Testing, and Remediation.  In:
    Proceedings of the  National Conference on
    Hazardous Wastes and Hazardous Materials,
    Atlanta, Georgia. March 1986. pp. 269-272.
 Adams, T. E.   Hydrocarbon Leakage Detection
    System and Apparatus.  Canadian Patent No.
    1,185,693. October 28,1985.

 Ainlay, J. A.  Leak Detector for Underground Storage
    Tanks.  U. S. Patent No. 4,474,054.  October 2,
    1984.

 American Petroleum Institute.  Cathodic Protection of
    Underground Petroleum  Storage Tanks and
    Piping Systems.  API Publication 1632. 1983.

 American Petroleum Institute.  Recommended
    Practice for Abandonment or Removal of Used
    Underground  Service  Station  Tanks.  API
    Publication 1604, March 1981.

 American Petroleum Institute.  Recommended
    Practice for the  Interior Lining of Existing
    Underground Storage Tanks.  API Publication
    1631. 1983.

 American Petroleum Institute.  Tank and Piping Leak
    Survey. February 1981.

 American  Petroleum Institute.  Underground Spill
    Cleanup Manual.  API Publication 1628.  June
    1980.

 Anonymous.  API, EPA Study Hydrocarbon Detection
    for  Underground  Tank Monitoring  Wells.
    Petroleum Marketer. May-June 1986. pp. 10-18.

 Anonymous. A Problem that Won't Go Away. National
    Petroleum News. September 1985. pp. 31-35.

 Anonymous. Choosing a Compatible Underground
    Storage Tank. The Hazardous Waste Consultant.
    September-October 1986.  pp. 1-14 to 1-17.

 Anonymous.  Data on Leaking Underground Storage
    Tanks  Presented in EPA Study.  The Hazardous
    Waste Consultant. November-December 1986.
    pp. 2-22 to 2-25.

 Anonymous.  Florida Finalizes Rules Regarding Tank
    Leaks, Is Second State to Act. National Petroleum
    News.  June 1984.  p.63.

' Anonymous.  How Hazardous Waste Tanks Fail. The
    Hazardous Waste Consultant. July-August 1986.
    pp. 1-6 to 109.

 Anonymous. Petro-Tite Evolves to  Find  Leaking
    Tanks. Petroleum Marketer. November-December
    1985.
                                             6-2

-------
Anonymous.  Reliable On-Line Monitoring for Better
   Effluent Control.  Process Eng., 73:74-75, May
   1980.

Anonymous.  Small Jobbers Endangered, Study
   Predicts; Tank Leak Mess Already is Wounding
   Some. National Petroleum News. March 1984.

Anonymous. Sohio Keeps Watch on Underground
   Tanks. Ground Water Monitoring Review.  Winter
   1986. p.14.

Anonymous. System Detects Underground  Leaks.
   Oilweek 31 (51) :23-24, January 1981.

Anonymous. Tank Audit Computer Detects Leak
   Rates.  Petroleum Marketer. May-June 1986.
   pp.41-43.

Anonymous. Underground Storage Tanks: Secondary
   Containment Methods Described. The Hazardous
   Waste Consultant.  November-December, 1985.
   pp. 1-28 to 1-31.

Askenaizer, D. J., W. Barcikowski, K. V. B. Jennings,
   and J. E. Sarna.  Development of a  Compliance
   Program for Underground  Tanks  Containing
   Hazardous  Substances.  Report to Southern
   California Edison Co., Contract No. 2742915.
   March 1985.

B. C.  Research. Report on Investigations and
   Research   to  Develop  a  Service  Station
   Underground Tank Leak Detector.   Petroleum
   Association for Conservation of the Canadian
   Environment (PACE), Report No. 81-3.

Bisque, R. E. Migration Rates of Volatiles from Buried
   Hydrocarbon Sources through Soil  Media.  In:
   Proceedings of  the NWWA/API  Petroleum
   Hydrocarbons  and Organic Chemicals in  Ground
   Water Conference, Houston, Texas.  November
    1984.

Blevins, M. L.,  and D.  E. Williams.  Management of
   Gasoline  Leaks—A  Positive Outlook.   In:
   Innovative  Means of Dealing with Potential
   Sources of Ground Water Contamination;
   Proceedings of the 7th National Ground Water
   Quality Symposium, Las  Vegas,  Nevada,
   September 1984. pp. 46-83. Published by NWWA,
   Worthington, Ohio.  1985.

Cheremisinoff, P. N.,  J. G. Casana,  and H. W.
   Pritchard. Special Report: Update on Underground
   Tanks. Pollution Engineering. August 1986.
Cheremisinoff,  P.  N., J. G. Casana,  and R. P.
   Ouellette.  Special Report: Underground Storage
   Tank Control.  Pollution Engineering.  February
   1986.

Dowd, R. M.  Leaking Underground Storage Tanks.
   Environmental Science and Technology. 18(10),
   1984.

Dragun, J., A. C.,Kuffner, and  R. W.  Schneiter.
   Transport and Transformations of  Organic
   Chemicals. Chem. Eng., 91(24):65-72,1984.

Eklund, B.  Detection of Hydrocarbons in Groundwater
   by Analysis  of  Shallow Soil Gas/Vapor.  API
   Publication No. 4394. May 1985.

Everett, L. G.,  E.  W.  Hoylman, L. G. Wilson,  and L. G.
   McMillion.  Constraints and Categories of Vadose
   Zone  Monitoring Devices.  Ground Water
   Monitoring Review 4(1):26-32, Winter 1984.

Fletcher, S.  Leaks in Storage  Tanks  Polluting
   Groundwater. Houston Post. December 1985.

Gerstenmaier, W. J., and J. A. Todd. Leak  Detection
   Systems and Method for Fluid Delivery Piping.
   U.S. Patent No. 4,131,216. December 26,1978.

Guest, R. J. Leak Detector and Method.  U.S. Patent
   No. 3,691,819.  September 19,1972.

Hazardous Waste Report-Trends  & Analyses.  The
   Next Regulatory Battle: Leaking  Underground
   Storage Tanks.  May 1984.

Hern, S. C.,  and S.  M.  Melancon.   Vadose Zone
   Modeling of Organic Pollutants. Lewis Publishers,
   Inc. 1986.

Hoick, J. N., and T. P.  Clark. Regulation  of
   Underground Storage Tanks in Minnesota. In:
   Proceedings of the 79th Annual Meeting of the Air
   Pollution Control Association.  Minneapolis,
   Minnesota. June 1986.

Horsley, S. W.,  and D. S. Blackmar.  Development
   and Implementation  of Regulations to Control
   Underground Fuel Storage Tanks  on Cape Cod.
   In: Proceedings of the 7th National Ground-Water
   Quality  Symposium,  Las  Vegas,  Nevada,
   September  1984.   National   Water   Well
   Association,  Worthington, Ohio. 1985. pp. 29-39.

Hubbard, G.  O.  Locating Holes  in Tubing.  U.  S.
   Patent No. 3,696,660.  October 10,1972.
                                              6-3

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Huebler, J,  E., and J, M. Craig.  Sonic Detection of
    Gas Leaks In  Underground Pipes. U.S. Patent
    No. 4,455,863. June 26,1984.

Jeyapalan, J.  K., and J.B. Hutchison.  Underground
    Storage Tanks-Leak Prevention,  Leak Detection,
    and Design.  In: Proceedings of the National
    Conference on Hazardous Wastes and Hazardous
    Materials, Atlanta, Georgia.  March 1986.

Kahn,  E.   Proposal  Gives  Muscle to  EPA on
    Underground Tank Rules.  Super  Service Station.
    April 1984.

Knopp,  P.  V.   Underground  Tank  Management.
    Pollution Engineering. December 1985. pp. 24-27.

Lund, T.  Corrosion of  Underground  Storage Tanks.
    Presented at HazPro '86,  Baltimore, Maryland.
    April 1986. Sponsored by Pollution Engineering.

Maresca Jr., J. W., P. C. Evans, R. A.  Padden, and R.
    E. Wanner.  Measurement of Small Leaks in
    Underground  Gasoline Storage Tanks Using
    Laser Interferometry. SRI international Project No.
    7637. September 1981.

Marketer's Report of  the Texas  Oil Marketers
    Association.    Why  Be  Concerned  about
    Underground Storage Tanks? June 1985.

McLean, F.  R.  Leak Seeking in Underground Tanks.
    Presented at the 43rd Annual Fire Department
    Instructors Conference, Kansas  City, Missouri.
    March-April 1971.

Milanovich, F.  P.   Detecting Chloro-organics In
    Groundwater. Environ. Sci. Technol. 20(5):41-42,
    1986.

Milke, G.  Method of and Apparatus for Locating Leak
    Areas of Pipe Lines, Especially Underground Pipe
    Lines. U. S.  Patent No. 3,722,261.

Murphy Jr., F. W., and B. G. Sparks. Remote Multiple
    Tank Liquid Level Measuring Device. U. S. Patent
    No. 4,064,752. December 27,1977.

Nacht, S. H. Underground Storage Tank Compatibility.
    Presented at HazPro '86,  Baltimore, Maryland.
    April 1986. Sponsored by Pollution Engineering.

National Fire Protection Association, Inc. Flammable
    and Combustible Liquids Code. NFPA Publication
    No. 30. 1984.
Petroleum  Equipment Institute. Future Trends In
    Petroleum Marketing  Operations. PEI Manual
    8342.
Plehn, S. W.  An  Introduction to LUST.
    Environmental Forum. July 1984.  pp. 5-9.
The
Predpall, D. F.,  W. Rogers, and A. Lamont.  An
    Underground Tank Spill Prevention Program.  In:
    Proceedings of Petroleum Hydrocarbons  and
    Organic Chemicals in Ground Water, Houston,
    Texas. November 1984. pp. 17-32.

Robbins, G. A.,  and M. M.  Gemmell.  Factoring
    Requiring Resolution in Installing Vadose Zone
    Monitoring Systems.  Ground Water Monitoring
    Review. Summer 1985.  pp. 75-80.

Robbins, R.  J.,  and D. G. Nichols.  Electric Leak
    Detection Systems  for Underground  Stored
    Chemicals and  Fuels.  In: Innovative Means of
    Dealing with Potential Sources of Ground Water
    Contamination;  Proceedings of the 7th National
    Ground Water Quality Symposium,  Las  Vegas,
    Nevada, September 1984. pp. 40-44. Published
    by NWWA, Worthington, Ohio. 1985.

Scheinfeld, R. A., and T. G. Schwendeman.   The
    Monitoring of Underground Storage Tanks-
    Current  Technology.   In: Proceedings of
    Petroleum Hydrocarbons and  Organic Chemicals
    in Ground Water, Houston,  Texas.  November
    1985.

Shaner, J. R.  Underground Tank  Dilemma: New
    Rules Could Cost Industry Billions. National
    Petroleum News. August 1984. pp. 36-39.

Singh,  P. N.  Case Study of Product Detection in
    Ground Water.  In: Proceedings of the  National
    Conference on Hazardous Wastes and Hazardous
    Materials, Atlanta,  Georgia.  March  1986.  pp.
    273-277.

Steel Tank Institute. Tank Talk. Bimonthly Newsletter
    (various issues).

Sun, M. EPA Grapples with Regulating Underground
    Storage Tanks.  Science, 233:518.

Tabary, J.  Underground Storage of  Petroleum
    Products. Pet. Rev. 27(318) :213-217, 1973.

The Hazardous and Solid Waste Amendments of 1984
    to the Resource Conservation and Recovery Act
    Subtitle 1, Sections 9001-9010 of U.S. Public Law
    98-616. November 1984.
                                              6-4

-------
Underwriters  Laboratories,  Inc.  Glass-Fiber-
   Reinforced Plastic Tanks for Underground Storage
   of Petroleum Products. UL Publication No. 1316.

Underwriters Laboratories, Inc.   Steel Underground
   Tanks for Flammable and Combustible Liquids.
   UL Publication No. 58.

Upton, H.  Tulsa  Letter.  Petroleum Equipment
   Institute Weekly Newsletter (various issues).

Utility Data Institute. Preliminary Characterization of
   Underground Storage Tanks Utilized by  Electric
   Utilities., December 1984.

Witherow,  W. E.  Epichlorohydrin in Secondary
   Containment Systems. In:  Innovative  Means of
   Dealing with  Potential Sources of Ground Water
   Contamination; Proceedings of the 7th National
   Ground Water  Quality Symposium, Las Vegas,
   Nevada, September 1984.  pp. 89-94.   Published
   by NWWA, Worthington, Ohio. 1985.

Wolder Engineering.  Southern California Edison
   Underground Tank Study, Rosemead, California.
   Wolder Engineering Project No.  B261-00.
   November 1985.

Young Jr., A.  D.  Underground Storage Tank Design
   State-of-the-Art for 1986. Presented at  HazPro
   '86, Baltimore, Maryland.  April 1936. Sponsored
   by Pollution Engineering.
                                                6-5

-------

-------
                              APPENDIX A
                             List of Vendors
 The following vendor list provides the address, phone number, and the name of the technical
representative for each company identified in this report as a vendor of leak monitoring devices.
                                     A-1

-------
Type of
Detector Company
Liquid Sensors
Grab Samplers
NEPCCO

Norton

(many others)
Chemical-Sensitive Paste
Kolor Kut
Products
McCabe

Interface Probe Monitor
Comar, Inc.


EMTEK, Inc.

Marine Moisture
Control
Oil Recovery
Systems, Inc.
Product Soluble Devices
EMTEK. Inc.

IFP Enterprise

In-Situ, Inc.

K&E Associates

Pump Engineer
Associates
Technology
2000, Inc.
Table A-1
List of Vendors
Technical
Address Representative

29 Wall Street
Foxboro, MA 02035
150DeyRoad
Wayne, NJ 07470


P.O. Box 541 5
Houston, TX 77262
76 Slope Dr.
Short Hills, NJ 07078

P.O. Box 832676
Richardson, TX 75083

27 Harvey Road
Bedford, NH 03201
60 Inip Dr.
Inwood, NY 11 696
220 Norwood Park S
Norwood, MA 02062

27 Harvey Road
Bedford, NH 031 02
680 Fifth Ave.
New York, NY 1001 9
21 OS. 3rd Street
Laramie, WY 82070
331 2 Industry Dr.
Long Beach, CA 90806
921 National Ave.
Addison, IL60101
265 Ballardvale St.
Wilmington, MA 01 887

Paul Guerra

..



D. Frauenberger

Joe McCabe


Bob Moorehead


Herold Solomon

Frank Giannone

Don Jones


Herold Solomon

C.E. Maier

Phil Gerhart

Jim Ridle

Matt Vetter

Donald Corey

Phone Number

617-543-8458

201-696-4700



713-926-4780

..


214-238-7691


603-627-3131

718-327-3430
800-645-7339
617-769-7600


603-627-3131

212-265-3800

307-742-8213

213-424-1517

312-543-2214

617-658-2900

Product Name

Liquid Samplers
and Bailers
Bailers



Water & Gasoline
Finding Pastes
Water & Gasoline
Indicator Pastes

•Models 807, 808
& 809 Tank Monitors
*PLD-17 Pipeline Monitor
Electronic Well Gauging
(EWGL-12) Light
Sonic Ullage
Interface Probe
Interface Probe


Detectron

Oil Fuse

Petrochemical
Release Monitors
PMS-800

Sentinel

TOLTECH Hydrocarbon
Monitor
Electrical Resistivity Sensors
Control
Devices
Total
Containment
2009-A West Detroit St.
Broken Arrow, OK 7401 2
15E. Uwchlan Ave.
Exton, PA 19341
Anthony Farque

Mike Webb

918-251-0387

215-524-9274

Wik-Stik

Total Containment
Cable-TC3000
A-2

-------
List of Vendors

Type of
Detector Company
*
Address
Thermal Conductivity Devices
FCI 1 755 LaCosta Meadows
San Marcos, CA 92069
Leak-X
Oil Recovery
Systems, Inc.
Pollulert
Systems
(Mallory)
Universal
Sensors and
Devices, Inc.
Vapor Sensors
Detector Tubers
MSA
National
Draeger, Inc.
Combustible Gas Detectors
MSA
Catalytic Sensor Devices
Bacharach
Instrument Inc.
Gas Tech, Inc.
Industrial
Scientific
Devices Corp.
Intek Corp.
Lumidor
Safety Products
Rexnord
Gas Detection
Products
560 Sylvan Ave.
Englewood Cliff, NJ 07632
220 Norwood Park South
Norwood, MA 02062
P.O. Box 706
Indianapolis, IN 46206
9205 Alabama Ave,
Unite
Chatsworth,CA91311
10770 Moss Ridge Rd.
Houston, TX 77043
P.O. Box 120
Pittsburgh, PA 15230
P.O. Box 426
Pittsburgh, PA 15230
625 Alpha Drive
Pittsburgh, PA 15238
8445 Central Ave.
Newark, CA 94560
355 Steubenville Pike
Oakdale, PA 15071
10410RockleyRd.
Houston, TX 77099
5364 NW 167th St.
Miami, Florida 3301 4
207 East Java Dr.
P.O. Box 3566
Sunnyvale, CA 94088

Technical
Representative
Malcolm McQueen
Bill Gelles
Don Jones
Wayne Pate
Wen Young
Patrick Kramer
Robert Dusch
Bruce Herman
Bill Milan
Bruce Holcom
Dave Kulawa
Ken Konrad
Norman Burnell
Greg Chambers

Phone Number
800-854-1993
615-744-6950
201-569-8989
617-769-7600
317-636-5353
818-998-7121
713-690-6268
800-672-2222
412-787-8383
412-967-3000
800-672-2222
412-963-2235
415-794-6200
412-788-4353
713-498-5855
305-625-651 1
408-734-1221

Product Name
785 Leak Detection
Systems
Leak-X System
CMS Variable
Level System
FD102andFD103
Leak Alert System
Samplair
Pump & Test Kit
Gas & Vapor
Detection Products
Several models
*TLV Sniffer
*Model 303
*Model H Gaspointer
Model 1238
LD-222
IGD
Model CRP-1
Combustible Gas
Detection System
A-3

-------
Type of
Detector
Company
Metal Oxide Semiconductors
API/Ronan












Armstrong
Monitoring
Azonic
Technology
Corp.
Calibrated
Instrument, Inc.
Enmet Corp.
Genelco, Inc.
Harco Corp.
International
Sensor Tech.
MSA
Oil Recovery
Systems, Inc.
Sierra Monitor
Universal
Sensors and
Devices, Inc.
U.S. Industrial
Products Co.
Product Permeable Devices
Teledyne
Geotech
Diffusion

W.L Gore
Sensors
Adsistor
Technology
Emco Wheaton
List
Address
12410 Benedict Ave.
Downey, CA 90242
215 Colonade Rd. South
Nepean, Ontario
Canada K2E 7K3
1671 Mabury Road
San Jose, CA 951 33
731 Saw Mill River Rd.
Ardsley, NY 10502
2308 S. Industrial Hwy.
Ann Arbor, Ml 481 04
11649 Chairman Dr.
Dallas, TX 75243
121 6 E. Tower Rd.
Schaumberg, IL60195
17771 Fitch St.
Irvine, CA 9271 4
600 Penn Center Blvd.
Pittsburgh, PA 15235
220 Norwood Park South
Norwood, MA 02062
1991 Tarob Court
Milpitas, CA 95035
9205 Alabama Ave.,
Unit C
Chatsworth, CA91311
13564 Pumice St.
Norwalk, CA 90650
3401 Shiloh Road
Garland, TX 75041
1 505 N. 4th St.
Flagstaff, AZ 86002
11300N.E.25thSt.
P.O. Box98115
Seattle, WA 981 25
Chamberlain Rd.
Conneaut, OH 44030
of Vendors
Technical
Representative
Matt Thomas
Bill Armstrong
Tom Gregory
John Mann
Elwood Boous
Michael Bouton
-
John Krell
Steve Long
Don Jones
Cathy Daigle
Wen S. Young
Samuel S. Wu
Philip Swiger
Art Molina
James Dolan
Chris Schauerman
Phone Number
--
—
408-729-4900
914-693-9232
313-761-1270
214-341-8410
312-882-3777
714-863-9999
412-776-8802
617-769-7600
408-262-661 1
818-998-7121
213-921-4342
214-271-2561
602-526-1290
206-523-6468
216-599-8151
Product Name
TRS 76
4200 Sensor
Enviro-Ranger
Pure Air Monitor
Several models
Soil Sentry
MultiRam12
AG5000&AG5100
Tankgard
VaporCMS
Model 201
Leak Alert
Tank Monitor
LASP System
LEAKLEARN
Adsistor Sensor
Leak Sensor II
Vapor Probe
A-4

-------
                                           List of Vendors
Type of
 Detector  Company
               Address
                       Technical
                       Representative
                 Phone Number   Product Name
Diffusion Sensors (cont.)
          EMMCp
          Enterprises

          Spearhead
          Tech., Inc.
               2525 Lehigh PI.
               Costa Mesa, CA 92626

               P.O. Box 51160
               Seattle, WA 98115
                       Tom Meany


                       Bill Michaluk
                 714-545-6030
                 604-688-8245
Env. Control Safety
Monitoring System

STI2X12lnground
Tank Monitor
PIDs
AID, Inc.
         Astro
         Resources

         HNU
          Photovac, Inc.
Portable  AID, Inc.
GCs

         HNU
FIDs
         Microsensor
         Technology Inc.

         Photovac, Inc.
         Sentex Sensing
         Tech., Inc.

         XON Tech
Foxboro
Analytical
Infrared   Foxboro
         Analytical

         Horiba
         Engineering
Rt. 41 & Newark Rd.
Avondale, PA 19311

100 Park Ave.
League City, TX 77573

160 Charlemont St.
Newton Highlands,
MA 02161

741 Park Ave.
Huntington,NY11743

Rt. 41 & Newark Rd.
Avondale, PA 19311

160 Charlemont St.
Newton Highlands,
MA 02161

41762 Christy St.
Fremont, CA 94538

739B Park Ave.
Long Island, NY 11743

553 Broad Ave.
Ridgefield, NJ 07657

6862 Hayvenhurst Ave.
VanNuys, CA91406

330 Neponset Ave.
Foxboro, MA 02035

330 Neponset Ave.
Foxboro, MA 02035

121 DuryeaAve.
Irvine, CA 92714
Chuck Sarnoski    215-268-3181   Model 580


PhilLandon       713-332-2484   Trace Gas
                                Analyzer-1010

Omar Gendron    617-964-6690   Model P1101
                                      Richard Smyth     516-351-5809   TIP "Underground
                                                                      Tank Monitor

                                      Chuck Sarnoski    215-268-3181   Model 590
                                      Bob Pelletier      617-964-6690   Models 201,
                                                                      301D and 501
                                      Bob Turner
                 415-490-0900   Michromonitor
                                      Richard Smyth     516-351 -5809   Photovac 10A10
                                      Donna lanuzzi     201-945-3694   Scentor
                                      Matt Young
                                                                818-787-7380   GC-810
Wendy Cotrell     617-543-8750   Century OVA


Wendy Cotrell     617-543-8750   Miran


Debbie Berardino   800-446-7422   IR Hydrocarbon
                                Gas Analyzer
                                                A-5

-------

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-------OCR error (c:\conversion\JobRoot\000002LU\tiff\20006GVE.tif): Unspecified error

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3.  Detection Capability (please specify units)
    3a. Lower detection limit (sensitivity)
       Can the sensitivity be adjusted, and if so, what is the range?
    3b.  Upper detection limit.
    3c.  Response Time_
           Lag Time _
           Rise Time.
           Fall Time
        Limitations (e.g., temperature) and their effect?.
    3d. Drift
    3e. Noise.
    3f.  Precision
    3g. What test procedures were used to test for the above parameters?.
    3h. How many sensors can operate from a single control box?.

    3i.  How often and for how long is each sensor on-line?	
    3j. Service Life of control box?	Sensors?.

 4. Experience
     4a. Is leak detector presently being marketed?	
        If yes, for how many years?	

     4b. How many of your detection systems are now in service?.

     4c. Has an actual leak ever been detected?	
     4d.  Describe the operating experience of system users..
                                           B-3

-------
        Potential maintenance problems (e.g., ice in well, electrical malfunction sensor
        deterioration)
        Cause and frequency of false negative readings?.
        Cause and frequency of false positive readings?
        Estimate and Describe repair/replacement experience for control boxes and sensors
        (if applicable)
5.  Cost Information

    5a. Capital cost of control box.

    5b. Capital cost per sensor	
    5c.  Installation cost of system for:  (assume 4-tank facility)

        New facility	

        Old facility	
        Existing monitoring well.

    5d.  Maintenance cost	
6.  Recommended Procedures

    6a. Describe installation procedures.
    6b. Is it necessary to install observation wells to use the detector?
                                          B-4

-------
6c. Can the leak detection system be retrofitted to existing facilities?.
6d. Are site characterization studies prior to installation necessary/recommended?.
6e. What type of utility service is required for installation and operation of the leak detection
    system?
6f.  Where should the leak detector be placed in relation to the tank?.
6g. What distance should separate sensors from the tank and each other?.
6h. How many sensors should be used per tank/excavation?.
 6i. Describe calibration procedures to be performed at time of installation.
 6j. What instrument settings are adjusted at time of installation (e.g., background
    adjustments)?
     Describe how and why this is done..
 6k. Can the system be operated in unsaturated, saturated (wet), and/or intermittent
     (saturated or unsaturated) soil condition? Specify!
 61.  Describe operating procedures.
                                        B-5

-------
 6m. Describe recommended operating environment (e.g., non-explosive atmosphere).
    Give allowable operating ranges for temperature, input voltage, etc.
6n. Maintenance requirements?
60. Maintenance schedule?
6p. Calibration procedures?.
6q. Calibration schedule?
6r.  Recommended sample flow rate and allowable variability?
6s. Is there any method to certify the performance of the system?	 If yes, include
    representative certification data and discuss how base-line values for certification
    were established.
6t.  Describe if and how the leak detect system differentiates between surface spills and
    underground leaks.
Please return completed survey form In the envelope provided to:
       Radian Corporation
       P.O. Box 9948
       Austin, TX 78766
       Attn: Mr. Bart Eklund (3)

Please direct any questions or comments to:
       Mr. Bart Eklund (512) 454-4797
       Mr. Walt Crow (512) 454-4797
                                     B-6

-------
                                        APPENDIX C
                                Tabulated Survey Results


C.1 Tabulated Results From Survey

The survey responses have been tabulated following the format of the questionnaire.  The tables give the
response from each vendor for each type of device. Results were summarized in Section 3. Where the vendor
left a question blank on the survey form, the term "No Response" or "N/R" is listed in the tables.  Where the
answer provided by the vendor was too lengthy or complicated to be tabulated, the term "Given" is listed in the
Tables C-1 through C-6.  Where vendors responded with multiple questionnaires describing similar products
based on the same principle of operation, answers are given for the most suitable gas leak detector (i.e., the
most sensitive or the least expensive). Products and companies listed in Table 3-1 as not having submitted a
survey form are omitted from these tables.

The estimated costs associated with each leak monitoring technique derived from the vendor responses are
given in Table C-5.  The installation costs provided by vendors are thought not to be based  on uniform
assumptions and therefore should not be directly compared.  Costs of well drilling, labor, utility service, cable,
etc., seem not to be addressed by some vendors.
                                                C-1

-------
 Type of Detector
                          Table C-1
             Vendor Responses for Principle of
          Operation of Leak Monitoring Techniques

 Company                   Principle of Operation
 Continuous Liquid-Phase
 Interface Probes       Comar, Inc.

 Product Soluble        EMTEK, Inc.
 Devices               In-Situ, Inc.

                      K&E Associates
                      Technology 2000, Inc.

 Electrical Resistivity    Total Containment
Thermal
Conductivity
 Leak-X
 Pollulert Systems (Mallory)
 Universal Sensors &
 Devices, Inc.
Intermittent Gas-Phase
Portable GC's




Infrared

PID's
 AID, Inc.
 HNU
 Photovac, Inc.
 XON Tech

 Horiba Engineering

 AID, Inc.
 Astro Resources Int.
 HNU
 Photovac, Inc.
Continuous Gas-Phase
Catalytic Sensors      Bacharach Instrument Co.

                      Industrial Scientific Devices

                      Intek Corp.
                      Rexnord Gas Detection
                      Products
Diffusion
Adsistor Technology
Emco Wheaton
EMMCO Enterprises
Spearhead Tech., Inc.
 Fiber optic sensor

 Softening of hydrocarbon-sensitive material/float-switch
 Destruction of sensing element by petrochemical/electrical
   contact
 Combined control system
 Softening of hydrocarbon-sensitive material/float-switch

 Deterioration of dielectric insulation on twisted pair of woven
  conductors

 Conduction
 AC Conductivity
 Thermal cooling
 Photoionization
 Photoionization
 Photoionization
 GC/Electron capture detector

 Non-dispersive infrared analysis

 Photoionization
 Photoionization
 Photoionization
 Photoionization
                            Catalytic combustion of explosive vapors on a platinum coated
                              bead
                            Catalytic bead platinum wire combustible sensor with
                              wheatstone bridge
                            Catalytic combustion of hydrocarbon vapors
                            Catalytic bead type combustible gas detection system
                                                  Adsorption sensor
                                                  Adsorption sensor
                                                  Physicochemical adsorption
                                                  Adsorption sensor
Metal Oxide
Semiconductors
Product Permeable
Devices
Armstrong Monitoring
Azonic Technology, Inc.
Calibrated Instrument, Inc.
Genelco, Inc.
MSA
Universal Sensors and
Devices, Inc.
U.S. Industrial Products

Teledyne Geotech
Cherrfical absorption on semiconductor material
Bulk semiconductor vapor sensor
Taguchi cell (metal-oxide semiconductor)
Aspirated vapor sensor
Metal-oxide semiconductor sensor
Metal-oxide semiconductor sensor

Solid-state sensor

Gas permeable cable, pump, and metal-oxide semiconductor
                                                   C-2

-------
Table C-2
Vendor Responses for Detection Specificity of Leak Monitoring Techniques
Detection
Type of Adjustable Potential False
Tvoeof Detects Compound For Specific Inter- Positive or
Detector Company Gas Liquid Detected Compounds ferences Negatives
Continous Liquid-Phase
Interface Comar, Inc. No Yes
Probes
Product EMTEK, Inc. No Yes
Soluble
Devices In-Situ, Inc. Yes Yes
K&E Assoc. Yes Yes
Technology No Yes
2000, Inc.
Electrical Total Yes Yes
Resistivity Containment
Thermal Leak-X No Yes
Conduc-
tivity Pollulert Yes Yes
Systems
(Mallory)
Universal No Yes
Sensors &
Devices, Inc.3
Intermittent Gas-Phase
Portable AID, Inc. Yes No
GC's
HNU Yes No
Photovac, Inc. Yes No
XON Tech Yes Yes

Infrared Horiba Yes No
Engineering
PID's AID, Inc. Yes No
Astro Yes No
Resources Int.
HNU Yes No

Photovac, Inc. Yes No

aThe questionnaire returned by Universal
metal-oxide semiconductor sensor. The
Hydrocarbons


-------
Vendor Responses for Detection
Type of
Detector
Continuous
Catalytic
Sensor



Diffusion



Metal Oxide
Semicon-
ductors




Detects
Company Gas Liquid
Gas-Phase
Bacharach Yes
Instrument
Co.
Industrial Yes
Scientific Devices
Intek Corp. Yes
Rexnord Gas Yes
Detection Products
Adsistor Yes
Technology
Emco Wheaton Yes
EMMCO Yes
Enterprises
Spearhead. Yes
Tech., inc.
Armstrong Yes
Monitoring
AzonicTech., Yes
Inc.
Calibrated Ins., Yes
Inc.
Genelco, Inc. Yes
MSA Yes
No
No
No
No
Yes
Yes
Yes
Yes
No
Yes
No
No
No
Universal No Yes
Sensors & Devices, Inc.3

Product
Permeable
Devices
U.S. Industrial Yes
Products Co.
Teledyne Yes
Geotech
No
No
•™™^^^™i™™""m*"««»™™<«i""'™^»^^^^^^^^^^^«^^^^^^B™^M^^^^m^^^^^m— ^^^^^ w^j2j^^5^^^^2™™^SSS™"S2
Table C-2
Specificity of Leak Monitoring Techniques (Continued)
Type of
Compound
Detected
Hydrocarbons
Hydrocarbons
HCs, H2, NH3
Hydrocarbons
Hydrocarbons
Hydrocarbons,
Acetone
Hydrocarbons
Given
Hydrocarbons
Given
Hydrocarbons
Hydrocarbons
Hydrocarbons
Hydrocarbons
Hydrocarbons
Hydrocarbons
Detection
Adjustable Potential
For Specific Inter-
Compounds ferences
No
No
No
Yes
Yes
No
Yes
Yes
No
Yes
No
No
No
No
Somewhat
No
H2O,CH4,
CO2,CO,
O2,S
Pb,Si,S,O2
Si.Esters,
Phosphates
HO.CI
None
H2S
None
None
CH4,S
CH4> H2O
CH4, H2O
CH4,CO
CH4,S,CO
CH4,CO
Sulfur
Compounds
None
False
Positive or
Negatives
Both
Both
Both
Both
None
n/a
None
No
Pos.
Both
Pos.
Neg.
Pos.
Pos.
Pos.
Yes
Severity of
Interferents
Only if
<10%O2
Variable
Variable
n/a
Gas Dis-
placement
Given
n/a
None
Only at
Explosive
Levels
Temporary
Given
Not
Specified
Normally low
n/r
Minimal
n/r
a The questionnaire returned by Universal gave a combined answer for both their thermal conductivity sensor and their
metal-oxide semiconductor sensor. The stated values are repeated in the table for both types of sensor.
======^^
C-4

-------
              Table C-3
    Vendor Responses for Detection
Capability of Leak Monitoring Techniques
Type of Detection Limit
Company Lower
Continuous Liquid-Phase
Interface Probe
Comar, Inc. 1 Qt.
Product Soluble Devices
EMTEK, Inc. <0.25 in.
In-Situ, Inc. 3.4mg/L Vap.
.079 mm Liq.
K&E Assoc. 1 00 ppm
Technology 1/64 in.
2000, Inc.
Electrical Resistivity
Total n/a
Containment
ThermalConductivity
Leak-X 5/8 in.
Pollulert Systems 1/8in.(liq)
(Mallory) 100ppm(gas)
Universal 200 ppm
Sensors &
Devices, Inc.
Intermittent Gas-Phase
Portable GC's
AID, Inc. 10ppb
HNU .001-1 ppm
Photovac, Inc. 1 ppb
XON Tech Variable
Infrared
Horiba 0-50 ppm
Engineering
PID's
AID, Inc. 0.1 ppm
Astro 0.1 ppm
Resources Int.
HNU .001-1 ppm
Photovac, Inc. 0.05 ppm
. .
Adjustable
No
No
Yes
Yes
No
Yes
Yes
Yes
No
No
Yes
Yes
Yes
Yes
No
n/r
Yes
Yes
Sensors
Par r.nntrnl
Upper Box
None 4
None 10
Unlimited 4
5,000 ppm 15
None 4
n/a 25 miles
of cable
8ft. 10
2 in. or 10-15
5,000 ppm
7,500 ppm 8-32
2,000 ppm 1
1.5-1 50 ppt 1
500 ppm 1
Variable n/a
100% 1
20,000 ppm 1
999.9 ppm 1
1.5-1 50 ppt 1
20,000 ppm 32
^M^KKl^H^WB^^^^^^^^^HHMBi^HnMM«mBi
Service
On-Line Control
Time Box
Continuous >3 Yrs.
Continuous Indefinite
Leak
Continuous >20 Yrs.
Continuous 7.5 Yrs.
Continuous 5 Yrs.
Continuous Indefinite
Continuous 3 Yrs.
Continuous 1 Yr.
(warrant)
Continuous >5 Yrs.
Continuous Not known
Continuous >5 Yrs.
n/a 5-10 Yrs.
n/a n/a
Continuous Indefinite
n/r Not known
Life
Sensors
>5 Yrs.
Until Detect
>20 Yrs.
12 Yrs.
Inspect
Annually
Indefinite
2 Yrs.
Many Yrs.
>8 Yrs.
1 0,000 Hrs.
>5 Yrs.
18 MO.
n/a
Indefinite
10,000 Hrs.
Continuous Unavailable 2yrs.
Continuous >5 Yrs.
4@ 5-10 Yrs.
(15sec/hr.)
>5 Yrs.
1 Yr.
                   C-5

-------
                                            Table C-3
                                 Vendor Responses for Detection
                       Capability of Leak Monitoring Techniques (continued)
Type of Detection Limit
Company Lower
Continuous Gas-Phase
Catalytic Sensors
Bacharach 50 ppm
Instrument
Industrial 0% LEL
Scientific
IntekCorp. 0.1%HC
Rexnord Gas 5% LFL
Detection
Products
Diffusion Sensors
Adsistor 1 00 ppm
Technology
Emco Wheaton 1 00 ppm
EMMCO List
Enterprises
Spearhead 1 00 ppm
Tech., Inc.
Metal Oxide Semi-Conductors
Armstrong ppm Range
Monitoring
Azonic 10-20 ppm
Technology Gasoline
Calibrated 1 ppm
Instrument
Genelco, Inc. 25 ppm
MSA 10 ppm
Universal 200 ppm
Sensors &
Devices, Inc.
Adjustable
No
n/r
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
No
Sensors
Upper Box
2,000 ppm 1
100% Lei n/a
LFL 4
LFL 1-8
100% No limit
100% 16
Pure liquid 10
100% 4 or 12
Cone.
Lower %'s 12
8,000 ppm 1
>500 ppm 1
8,000 ppm 1
n/a 4
7,500 ppm 8-32
Service
I On-Line Control
Time Box
Intermittent Indefinite
n/a n/a
Continuous n/a
Continuous 10Yrs.
u/sec n/r
Continuous 10Yrs.
Continuous Indefinite
Continuous 1 0 Yrs.
Continuous 20 Yrs.
32 min 5-7 Yrs.
Intervals
n/r n/r
7 min./? 5-10 Yrs.
Continuous >10Yrs.
Continuous >5 Yrs.
Life
Sensors
>1 Yr.
1 Yr.
1-10 Yrs.
2-3 Yrs.
>10Yrs.
>10Yrs.
Indefinite
>10Yrs.
10 Yrs.
40 Hrs.
@ 1 .5 yrs.
5 Yrs.
>5 Yrs.
>8 Yrs.
    U. S. Industrial   2 ppm        No         100% Lei    16
    Products Co.

Product Permeable
    Teledyne       <20ppm       n/r         n/r         1
    Geotech
Continuous  >10Yrs.    >3Yrs.
Adjustable   Not known   5 Yrs.
                                              C-6

-------
Table C-3
Vendor Responses for Detection
Capability of Leak Monitoring Techniques (Continued)
Type of Detector/ Response Lag Rise Fall Test
Company Time Time Time Time Drift Noise Precision Procedures
Continuous Liquid-Phase
Interface
Comar, Inc. @ 30 min. n/a n/a
Product Soluble Devices
EMTEK, Inc. Instant <1 min. n/a
In-Situ, Inc. 0.5-23 n/a n/a
min. (liq.)
K&EAssoc. 5 sec. NIL <.5sec.
Technology Variable n/a n/a
2000, Inc.
Electrical Resistivity
Total Contain. Given Given Given
Thermal Conductivity Devices
Leak-X Immediate 5 sec. n/a
Pollulert Instant Instant Instant
Systems (Mallory)
Universal Instant <1 MIN.
Sensors & Devices, Inc.
Intermittent Gas-Phase
Portable GC's
AID, Inc. Variable n/r n/r
HNU <3sec Negl. Negl.
Photovac, 1-10 min. 1 min. 1 min.
Inc.
XONTech n/a n/a n/a
Infrared
Horiba 30 sec. 30 sec. 30 sec.
Engineering
PID's
AID, Inc. 3 sec. Var. Var.
Astro Instant n/r n/r
Resources Int.
HNU <3sec Negl. Negl.
Photovac, 3 sec. 5 sec. 3 sec.
Inc.
n/a None None 100% Yes
n/a n/a n/a n/a n/a
n/a None None n/r Ind. Lab
<6min. None None 1.1% Cycle Test.
n/a n/a n/a n/a Given
Given n/a n/a n/a Given
n/a n/a n/a n/a NBS.UL.etc.
Instant n/a n/a Given Given
<3MIN. +/-10% +/-2% +/1 10% Given
n/r Minimal Minimal Var. Std. Gas
Negl. <1 % <1 % +/- 1 0% Known
Samples
1 min. Compen- 1 :4 3-5% Std. Gas
sated
n/a Minimal Minimal Good Std. Gas
30 sec. 2%/Day 1%of 1%of Std. Gas
Full Scale Full Scale
Var. Not Not Var. Std. Gas
Known Known
n/r n/a n/a 0.1 ppm Propylene
(gas)
Negl. <1 % <1 % +/- 1 0% Known
Samples
7 sec. 1 ppm/hr. 0.1 ppm 1% Std. Gas
Limitations I
None
>32F
Temp.
Tests
-
Temp.
Given
Liq. Only
Temp.
Temp. &
Humidity
Temp.
n/r
Temp.
-
Temp.
Temp.
Temp.
n/r
Temp, or
Humidity
C-7

-------
Table C-3
Vendor Responses for Detection
Capability of Leak Monitoring Techniques (Continued)
Type of Detector/ Response Lag Rise
Company Time Time Time
Continuous Gas-Phase
Catalytic Sensor Devices
Bacharach 30 sec. n/r n/r
Instrument Co.
Industrial 12 sec. n/r n/r
Scientific Devices
IntekCorp. 10 sec. 2-3 sec. 7 sec.
Rexnord <20sec. n/a n/a
Gas Detection
Products
Diffusion Sensors
Adsistor 1 sec. msec. msec.
Technology
Emco 5 sec. 5 sec. 5 sec.
Wheaton
EMMCO - - instant
Enterprises
Spearhead Given Given Given
Tech., Inc.
Metal Oxide Semiconductors
Armstrong Immed. n/a n/a
Monitoring
Azonic 20 sec. n/r n/r
Tech. Corp.
Calibrated <1 sec. <1 sec. <1 sec.
Instrument, Inc.
Genelco, Inc. Immed. Immed. 20 sec.
MSA <1 0 sec. <1 sec. <1 0 sec.
Universal -- Instant <1 MIN.
Sensors
and Devices, Inc.
U.S. 30 sec. 3-10 sec. 5 sec.
Industrial
Products Co.
Product Permeable Devices
Teledyne n/r n/r n/r
Geotech
Fall
Time Drift Noise
n/r +/-250ppm 0-50
for 10 min. ppm
n/r n/r n/r
20 sec. 2% 1%LFL
LFL/mo.
<30 sec. Negl. n/a
seconds No No
15 sec. n/a Compen-
sated
Var. None Compen-
sated
Given None None
30 sec. +/- 8% NIL
n/r 1 uV/C 120dB
<1 sec. Not Not
Known Known
< 15 min n/r n/r
<10sec. n/a n/a
<3 MIN. +/-10% +1-2%
45-60 sec. <5%/Yr. No
n/r n/r n/r
Precision
+/- 5%
1%
+/- 5%
+/- 3%
Yes
n/a
+/-10mV
Unspeci-
fied
+/- 8%
1%
Not
Known
n/r
n/a
+/1 10%
2%
n/r
Test Pro-
cedures
Factory
Testing
n/r
Standard
Given
Various
Std. Gas
Yes
Given
Confiden-
tial
Factory
Test
Lab Tests
Gas Stds.
n/a
Given
n/a
n/r
Limit-
ations
25 min.
warm-up
Temp.
None
-
High
Temps
Temp.
n/a
Given
NIL
n/r
Temp.
n/r
None
Temp. &
Humidity
n/a
n/r


C-8

-------
1 	
Vendor Responses
Type of Product
Detector/ On
Company Market
Continuous Liquid-Phase
Interface Probe
Comar, Inc. Yes
Product Soluble Devices
EMTEK, Inc. Yes
In-Situ, Inc. Yes
K&E Assoc. Yes
Technology, Yes
2000, Inc.
Electrical Resistivity
Total Yes
Containment
Thermal Conductivity
Leak-X Yes
Pollulert Yes
Systems (Mallory)
Universal Yes
Devices, Inc.
Intermittent Gas-Phase
Portable GC's
AID, Inc. Yes
HNU Yes
Photovac, Inc. Yes
XON Tech Yes
Infrared
Horiba Yes
Engineering
PID's
AID, Inc. Yes
Astro No
Resources Int.
HNU Yes
Years
On
Market
1/2
1
1/4
2
1/4
15
10
Not
Given
2
1
8-10
10
6
10
7
n/r
8-10
•
Table C-4
for Experience of Leak Monitoring Techniques
No. in
Service
12
3
0
200
0
400-500
1000's
Has Leak
Been
Found?
No
Yes
No
Yes
No
Yes
Yes-
Many
1000's Yes
1,300
10
@ 3,500
100's
@50
100's
n/r
Unavailable
@ 3,500
Yes
Yes
Yes
Yes
Not
known
Yes
Yes
Yes
Yes
Maint.
Problems
None
Ice
None
Ice, Elec.
Severe
Deterioration
None
Improper
Installation
Cleaning
None
Columns
Water
Columns
Not
known
n/a
Water, Dirt
Calibration
Water
Cause of
False
Negatives
Break in
Cable
n/a
n/a
n/a
None
None
Elec.
Short
No
Response
Not
Known
None
Application
Dependent
Not likely
Not known
n/a
Moisture
n/a
Application
Dependent
Cause of
False
Positives
n/a
n/a
n/a
Back-
ground
Mech.
Failure
None
n/a
No
Response
Not
Known
None
Application
Dependent
Interferences
Not known
Interferences
Not known
Interferences
From Gases
Application
Dependent
C-9

-------
„  „                          Table C-4
vendor Responses for Experience of Leak Monitoring Techniques (continued)
Type of Product Years
Detector/ On On
If Company Market Market
PID's(cont.)
Photovac, Inc. No 2 (TIP)
Continuous Gas-Phase
Catalytic Sensors Devices
Bacharach Yes 1
Instrument Co.
Industrial Yes 5
| Scientific Devices
1
Intek Corp. Compo- 7
nent Only
RexnordGas Yes 15
Detection Pds.
Diffusion Sensors
Adsistor Yes 10-20
Technology
EmcoWheaton Yes 1.5
EMMCO Yes 12
Enterprises
Spearhead Yes Given
Tech., Inc.
Metal Oxide Semiconductors
Armstrong Yes 5
Monitoring
Azonic Yes 0.5-1
Tech. Corp.
Calibrated Yes 12
Instrument, Inc.
Genelco, Inc. Yes 1.5
MSA Yes Just
Started
Universal Yes 2
Sensors & Devices, Inc.
U.S. Industrial Yes 1
Products Co.
Product Permeable Devices
Teledyne Yes 4
Geotech
No. in
Service
100's
100
n/r
>20,000
>50,000
75,000
200
0
(50,000)
35
n/a
10-15
Not
Known
30
Test Units
Only
1,300
n/a
1 (tank)
4 (pipeline)
Has Leak
Been
Found?
Yes
Yes
Yes
Yes
Yes
2 In
Ground
Yes
Yes
Yes
Yes
Yes
n/r
Yes
Yes
Yes
n/a
Yes
Maint.
Problems
Dust Filter
None
None
Several
(given)
Several
(given)
n/a
n/a
0-60 C
Given
None
To Date
Several
Listed
n/r
None
Observed
None
Given
n/a
Given
Cause of
False
Negatives
None
?
None
No specific
Zero Drift
VAC
n/a
None
None
None
Old Sensor
Several
(<1%)
n/r
None
To Date
None
Known
Not
Known
Temperature
Sensor Break
Cause of
False
Positives
Interferences
Below 100ppm
Interferences
None
No specific
Temperature
n/a
None
Electrical
Malfunction
Given
n/a
<1%
n/r
None
To Date
None
To Date
Not
Known
No
:
n/a
^^ 	 	 	
                               C-10

-------
^-sssssss^s^s^sss^^^s^ss^ss^ssssss^ss^sss^sss^sss
Table C-5
Vendor Responses for Cost of Leak Monitoring Techniques
Type of Capital Costs Installation Costs -$ (4 Tanks)
Company Control Box
Continuous Liquid-Phase
Interface Probe
Comar, Inc. 1 ,200
Product Soluble Devices
EMTEK, Inc. 1,195

In-Situ. Inc. 395

K&E 1,175
Associates
Technology 1,400
2000, Inc.
Electrical Resistivity
Total 1,495
Containment
Thermal Conductivity Devices
Leak-X 1,400
Pollulert Systs. n/r
(Mallory)
Universal 1,000-1,600
Sensors & Devices, Inc.
Intermittent Gas-Phase
Portable GC's
AID, Inc. 5,850
HNU n/r
Photovac, Inc. 8,000
- 14,000
XON Tech n/a
Infrared
Horiba 1,750
Engineering - 9,000
PID's
AID, Inc. 3,880
Astro 4,125
Resources Int.
HNU n/r
Photovac, Inc. 6,300
Sensor

200
260-DW Tank

195-245

475

900

85-185

625-725
n/r
200-800


398
n/r
n/a

5,000-12,000

n/a


398
1,675

n/r
200
New Facility

1,200
>2,200
600-Well
1,500-2,000

>2,500

11,000

2,820

2,500
Minimal
1,400


Var.
@20,000
Var.

n/a

1,750-30,000


Not Known
n/r

@ 20.000
n/r
Old Facility

1,200
>3,600

3,000
- 7,000
>4,500

7,000
- 1 1 ,000
5,520

5,500
Var.
4,900


Var.
@ 20.000
Var.

n/a

1.750
- 30,000

Not Known
n/r

@ 20,000
7,500
Old Well

200
>3,600

1,500
- 2,000
500

7,000

3,320

4,200
Same As
Equipment
1,600


None
@ 20,000
Var.

n/a

n/r


None
n/r

@ 20.000
7,000
======
Maintenance
Cost$

NIL
None

None

<50/Yr.

100

n/r

600/Yr.
2 Man Hours
300/Yr.


Minimal
<5%/Yr.
600/Yr.

Not Known

Var.


Minimal
n/r

<5%/Yr.
600/Yr.
C-11

-------
	 • l^^>^^^^HMIKi^HMNWHMMtt«MH«HMHBnnM^^MnMI^^Hil^MM^HMIM^H^^^MHH^MMM
Table C-5
Vendor Responses for Cost of Leak Monitoring Techniques (Continued)
Type of Capital Costs
Company Control Box
Continuous Gas-Phase
Catalytic Sensor Devices
Bacharach 895
Instrument Co.
Industrial n/a
Scientific Devices
Intek Corp. 950-1 ,300
Rexnord Gas 700-2,400
Detection Products
Diffusion Sensors
Adsistor n/a
Technology
Emco Wheaton 1 ,400
EMMCO 1,950
Enterprises - 4,200
Spearhead 2,450
Tech., Inc. - 3,540
Metal Oxide Semiconductors
Armstrong 420
Monitoring
Azonic 1 ,500
Technology - 4,000
Corp.
Calibrated <1 ,000
Instrument, Inc.
Genelco, Inc. 1,500
- 4,000
MSA 985
Universal 1,000
Sensors & -1,600
Devices, Inc.
U.S. Industrial >1,300
Products Co.
Product Permeable Devices
Teledyne 5,000
Geotech
Sensor
65
<100
@180
125
n/a
200
250
200-300
28
1,000-1,500
n/r
Included
94
200-800
145
6/ft.
Installation Costs - $ (4 Tanks)
New Facility Old Facility Old Well Cost $
n/a n/a n/a n/r
n/a n/a n/a n/a
n/r n/r n/r n/r
Same As Same As Same As Low
Equip. Cost Equip. Cost Equip. Cost
n/a n/a n/a n/a
Given Given Given Minimal
>3,700 >3,700 >3,500 0-150/Mo.
1,000-1,200 3,000 1,200-1,500 1,400/Yr.
NIL
3,000-7,500 3,000-7,500 3,000-4,700 300/Yr.
n/r n/r n/r n/r
Var. Var. Var. Var.
NotEstab. NotEstab. n/r Near Zero
1,400 4,900 1,600 300/Yr.
n/a n/a 3,200-3,600 n/a
n/r n/r n/r Negl.
===!==s=========^^ 	 -----
C-12

-------
Table C-6
Vendor Responses For Recommended
Procedures For Leak Monitoring Devices
Type of
Detector/
Company
Are Wells
Required?
Continuous Liquid-Phase
Interface Probe
Comar, Inc. Yes
Product Soluble Devices
EMTEK, Inc.
In-Situ, Inc.
K&E Assoc.
Technology
2000, Inc.
Electrical Resistivity
Total
Containment
Yes or
DWTank
No
Yes
No
Yes
ThermalConductivity Devices
Leak-X Yes
Pollulert
Systems (Mallory)
Universal
Yes
Yes
Can
System be
Retrofitted?
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Recommend
Site Study
Unnecessary
Yes
Yes
No
Yes
Yes
Yes
As Required
Yes
Utility
Service
None
11 5/230 V
60Hz
None
120 VAC
110VAC
11 0-1 20 VAC,
50/60 Hz
120 VAC
110V
115VAC
Location
To Tank
Downgradient
4 Corners
Downgradient
-
Downgradient
In Excavation
2 Ft. Below
2 Ft. Below
Within 15 Ft.
Distance
From Tank
Perimeter
VAR.
VAR.
Within 5 Ft.
Close
2 Ft.
2 Ft.
Close
<15Ft.
Sensors & Devices, Inc.
Intermittent Gas-Phase
Portable GC's
AID, Inc.
HNU
Photovac, Inc.
XON Tech
Infrared
Horiba
Engineering
PID's
AID, Inc.
Astro
Resources Int.
HNU
Photovac, Inc.



No
No
No
Not Known

Yes

Yes
n/a

No
Yes



Yes
Yes
Yes
Not Known

Yes

Yes
Yes

Yes
Yes



Yes
Yes
Yes
Not Known

No

Yes


Yes
No



10VAC,
12VDC
110V, 60Hz
None
110V

115V,60Hz

None
AC Power

110V.60HZ
110 VAC



n/a
Up To User
Downgradient
Not Known

n/a

n/a
As close as
Possible
Up to User
Above Water
Table


100 Ft.
n/a
n/a
VAR.

n/a

n/a
20-30 Ft.

h/a
50 Ft.

C-13

-------
Table C-6
Vendor Responses For Recommended
Procedures For Leak Monitoring Devices (Continued)
Type of
Detector/
Company
Continuous Gas-Phase
Catalytic Sensor Devices
Bacharach
Instrument Co.
Industrial
Scientific Devices
Intek Corp.
Rexnord Gas
Detection Products
Diffusion Sensors
Adsistor
Technology
Emco Wheaton
EMMCO
Enterprises
Spearhead
Tech., Inc.
Are Wells
Required?
Yes
(Barhole)
n/a
Sometimes
n/a
Sometimes
Yes
No
Metal Oxide Semiconductors
Armstrong No
Monitoring
Azonic
Technology Corp.
Calibrated
Instrument, Inc.
Genelco, Inc.
MSA
Universal
Sensors &
Devices, Inc.
U.S. Industrial
Products Co.
Yes
n/r
No
Yes
Yes
No
Product Permeable Devices
Teledyne No
Geotech
Can
System be
Retrofitted?
Yes
n/a
Yes
n/a
Yes
Yes
Yes
Yes
Yes
n/r
Yes
Yes
Yes
No
Yes
Recommend
Site Study
No
n/a
Yes
n/a
Yes
Yes
Yes
Yes
Yes
n/r
Yes
No
Yes
No,
Yes
Utility
Service
None
n/a
„ 1 1«
1 1 VAC or
20-28 DC
n/a
115 VAC
<15AMP
VAR.
Given
110-120VAC,
60Hz
None
n/r
115 VAC
Elec Power
115VAC
~
n/r
Location
To Tank
n/r
n/a
VAR.
n/a
Above Water
Table
Under
Given
In
Excavation
Backfill
n/r
See Manual
See Manual
Within 15 Ft.
Given
As Close as
Possible
Distance
From Tank
n/r
n/a
VAR.
n/a
Variable
Close
Proximity
Given
1 Ft. Below
None
Specified
n/r
1 Ft.
See Manual
<15Ft.
1 Ft.
n/r
C-14

-------
Table C-6
Vendor Responses For Recommended
Procedures For Leak Monitoring Devices (Continued)
Type of
Detector/
Company
No. of
Sensors
Per Tank

Calibration
Procedures
Adjustable
Instrument
Settings

Use In
Wet Soil

Operating
Environment

Temperature
Range

Voltage
Range
Continuous Liquid-Phase
Interface Probe
Comar, Inc.
Product Soluble
EMTEK, Inc.
In-Situ, Inc.
K&E Assoc.
Technology
2000, Inc.
Electrical Resistivity
Total
Containment
Thermal Conductivity
Leak-X
Pollulert Systs.
(Mallory)
Universal

1-4

4
Var.
1-4
4


4

None

Pump Test
None
Given
Given


None

None

None
None
Yes
None


None

Yes

Yes
Yes
Yes
Yes


Yes

Any

Syst. is Safe
Any
n/a
Given


Any

-50°-140°F

None Given
No Limits
30" -1 20° F
-4°-122°F


32° -250° F

n/a

None Given
n/a
85-1 35V
95-1 30 Vac


11 0-1 20 Vac
120° -150° (cable)

Every 15 Ft.
4

Every 15 Ft.

None
None

None

None
None

Trimpots

Yes
Yes

Yes

Any
Given

Non-explosive

-40° - 50° C
-40° - 50° C

32°-125°F

100-1 40 Vac
100-1 40 Vac

105-1 25 Vac
Sensors & Devices, Inc.
Intermittent Gas-Phase
Portable GC's
AID, Inc.
HNU
Photovac, Inc.

XON Tech
Infrared
Horiba
Engineering
PID's
AID, Inc.

Astro
Resources Int.
HNU
Photovac, Inc.

1
1 or more
1

Not known

n/a


n/a

Var.

1 or more
1-6

Gas Std.
n/a
Cal. Gas

Cal. Gas

Std. Gas


Cal. Gas

N2+C3H8
Gas Stds
n/a
Cal. Gas

None
Zero/Span
Several

Not known

Zero/Span


None

Zero/Span

Zero/Span
Several

Yes
Yes
Yes

Yes

Yes


Yes

Yes

Yes
Yes

Non-explosive
Given
Non-explosive

Room Temp.

Given


Non-explosive

Clean, Temp
Controlled
Given
Given

0°-40°F
n/r
40°-120°F

RT-200° C

Given


0° - 45° C

-10°-+50°C

n/r
30 °-1 20° F

n/r
n/r
115 AC or
12V DC
110V

11 0-1 30V


115 Vac,
12V DC
110Vac,
60Hz
n/r
1 10-120 V
C-15

-------
Table C-6
Vendor Responses For Recommended
Procedures For Leak Monitoring Devices (Continued)
Type of No. of
Detector/ Sensors
Company Per Tank
Continuous Gas-Phase
Catalytic Sensor Devices
Bacharach n/r
Instrument Co.
Industrial n/a
Scientific Devices



Rexnord Gas Var.
Detection Prods.
Diffusion Sensors
Adsistor n/a
Technology
Emco Wheaton 1 or more

EMMCO 1 or more
Enterprises
Spearhead Given
Tech., Inc.
Metal Oxide Semiconductors
Armstrong 1 -2
Monitoring
AzonicTech. 1-2
Corp.
Calibrated n/r
Instrument, Inc.
Genelco, Inc. 2
MSA 4

Universal Every 1 5 Ft.
Sensors &
Devices, Inc.
U.S. Indust. 1-2
Products Co.
Product Permeable Devices
Teledyne 2
Geotech

Calibration
Procedures


Cal. Kit

n/a

Adjustable
Instrument
Settings


Several

n/a




See
Manual

n/a

None

"A"
Constant
Given


n/a

See
Manual
n/r

Self-Calibrat
See Manual

None


Zero/Span


None



None


n/a

Trip point

"A"
Constant
Given


None

See
Manual
n/r

Several
Several

Trimpots


None


Gain/Zero


Use In
Wet Soil


Yes

n/a

•^


Yes


n/a

Yes

Yes

Yes


Yes

Not in
Saturated
n/r

Yes
Yes

Yes


Yes


Yes


Operating
Environment


Intrinsically
Safe
Any

OK for
Hazardous
Controller in
Non-hazard.

Air

Controller in
Non-hazard.
NFPA Classl

Air


Non-
explosive
Non-
explosive
n/r

Indoors
Intrinsically
Safe
Non-
explosive

Given


Any


Temperature
Range


-4°- 122° F

-10°-45°C

-20° - 60« c

-40° - 85° C


-100°-160°F

-40° - 70° C

Not Specified

-100°-160°F


n/r

0°-125°C

n/r

Not Specified
-5°-140°F

32°-125°F


-10°- 150° C


n/r


Voltage
Range


n/a

n/a

n/r

105-1 30 Vac
20-28 DC

mV-12V

n/r

105-1 25 Vac

110V


n/r

n/r

n/r

105-1 25 Vac
11 0-1 25 Vac

105-1 25 Vac


3VDC


n/r

C-16

-------
Table C-6
Vendor Responses For Recommended
Procedures For Leak Monitoring Devices (Continued)
Type of
Detector/ Maintenance
Company Requirements
Continuous Liquid-Phase
Interface
Comar, Inc. None
Product Soluble
EMTEK, Inc. n/a
In-Situ, Inc. Inspect
K&E System Test
Associates
Technology Inspect
2000, Inc.
Electrical Resistivity
Total None
Containment
Thermal Conductivity
Leak-X Inspect
Pollulert Systs. Clean Probes
(Mallory)
Universal Not Given
Sensors & Devices, Inc.
Intermittent Gas-Phase
Portable GC's
AID, Inc. Given
HNU n/r
Photovac, Inc. Given
XON Tech Minimal
Infrared
Horiba Day/Month
Engineering
PID's
AID, Inc. Clean Lamp
Astro Calibration
Resources Int.
HNU n/r
Photovac, Given
Inc.
Maintenance
Schedule
2Yrs.
n/a
Weekly
For 1 min.
As Required
Annual
None
60 days
As Required
4/Yr.
Before Use
n/r
6 Mo.
Minimal
Monthly
Given
Daily
n/r
6 Mo.
Calibration
Procedures
None
n/a
None
n/a
None
None
None
None
None
Gas Std.
n/r
Automatic
Std. Gas
Day/Month
Zero/Span
Daily
n/r
Automatic
Calibration
Schedule
n/a
n/a
None
n/a
None
None
None
None
None
Before Use
n/r
1/Hr.
Var.
Day/Month
Daily
Daily
n/r
1/Day
Flow
Rate
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
0.010L/min.
n/r
n/a
Var.
0.5-1.5
L/min.
0.3-0.6
L/min.
0.05-0.5
L/min.
n/r
n/a
Certification
No
n/a
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Use Stds.
Use Stds.
Use Stds.
Calibr.
Yes
Use Stds.
No
Use Stds.
Given
Differentiates
Surface Vs.
Underground
No
n/a
No
No
No
No
No
No
n/a
Yes
By Placement
No
No
No
Yes
No
By Placement
No
C-17

-------
Table C-6
Vendor Responses For Recommended
Procedures For Leak Monitoring Devices (Continued)
Type of
Detector/ Maintenance Maintenance
Company Requirements Schedule
Continuous Gas-Phase
Catalytic Sensor Devices
Bacharach Std. Gas n/r
Instrument Co.
Industrial Calibration None
Scientific
Devices
Intek Corp. Calibration Var.
Rexnord Gas Calibration 4/Yr.
Detection Prods.
Diffusion Sensors
Adsistor None None
Technology
Emco Annual Test Annual
Wheaton
EMMCO Self testing Self Testing
Enterprises
Spearhead Given 4/Yr.
Tech., Inc.
Metal Oxide Semiconductors
Armstrong None Not Needed
Monitoring
AzonicTech. Clean 1-2/Yr.
Corp.
Calibrated n/r n/r
Instrument, Inc.
Genelco, Inc. 6 Mo. 6 Mo.
MSA None n/a
Universal Not Given 4/Yr.
Sensors & Devices, Inc.
U.S. Industrial Minimal 6 Mo.
Products Co.
Product Permeable Devices
Teledyne n/r n/r
Geotech
Calibration
Procedures
n/r
Std. Gas
Var.
See
Manual
Yes
None
Resistance
Test
Given
Gas Std.
See Manual
n/r
Self-
Calibration
See
Manual
None
6 Mo.
n/r
Calibration
Schedule
Check
Before Use
Check
Before Use
n/r
4/Yr.
Once
n/a
Not
Established
Given
When Sens.
Replaced
During
Maintenance
n/r
None
4/Yr.
None
At Install.
n/r
Flow
Rate
>1.2SCFH
n/a
1 L/min.
(+/- 50%)
2 Ft3/Hr.
n/a
n/a
n/a
n/a
n/a
2 L/min.
n/r
2 L/min.
n/a
n/a
n/a
0.7-1.1
L/min.
Differentiates
Surface Vs.
Certification Underground
Cert. Gas No
n/r n/a
Zero/Span n/r
Yes No
Yes By Location
Yes No
Yes No
Given Given
Cal-kits No
Yes Yes
n/r n/r
Yes Yes
n/a No
Yes n/a
n/a n/a
n/r n/r

C-18

-------
                                  GLOSSARY OF TERMS
       The purpose of this section is to provide definitions related to proper interpretations of this report.
Accuracy is the degree of agreement between the
    measured value and the "true" value; it includes
    components of bias (systematic error) and
    precision (random error).

Anode is the electrode at which oxidation (electron
    releasing)  reactions  occur.  The anode is
    electrically  connected  to a cathode  (see
    definition) where  the  released electrons are
    consumed. In the process of corrosion, the anode
    is the place where  metal oxidizes to positive ions
    which dissolve in the electrolyte. The anode may
    be a separate piece of metai, as when steel is
    connected to brass  (see galvanic corrosion), or it
    may be  an area on a  freely corroding surface
    which develops a slight positive potential relative
    to the rest of the metal because of metallurgical or
    environmental variations.  Metal is eaten away at
    this location.  Anodes  in impressed current
    cathodic protection systems are not necessarily
    metallic, but must be electrical conductors.

Annular space is the  space  between the inner and
    outer walls of a double-wall tank or pipe.

Aquifer refers  to  subsurface strata containing
    sufficient groundwater so that  the water can be
    pumped out.

Area-wide  surveillance techniques  refer to a
    number of methods used to identify the location of
    a leak or to delineate an area of contamination.
    They involve systematically making a number of
    measurements over a large area.

Automatic level sensor refers to an instrument used
    for inventory control to provide unattended,
    product volume  measurements.

Background  contamination  is any residual
    concentration of the  analyte of interest that may
    be present at a site.

Calibration schedule  is the frequency of inspection
    and adjustments  required to  ensure reliable
    detector performance.
Cathode is an electrode where reduction (electron
   consuming) reactions occur.  No corrosion (metal
   loss) occurs at cathodes.

Cathodic protection is a technique for reducing the
   rate of corrosion of a metal by artificially making it
   the cathode  of an  electrochemical corrosion cell
   by  application of direct current.  There are two
   fundamental kinds of cathodic protection systems:
   sacrificial anode systems and impressed current
   systems.  Sacrificial anode systems consist of
   anodes of active metals like zinc, magnesium, or
   aluminum  connected to the structure to be
   protected.  The active metal corrodes away and
   releases  electrons into the structure to be
   protected; in this way,  the structure becomes  a
   cathode. The anodes which are consumed over
   time  are  "sacrificial"  and  must be replaced
   periodically.  Impressed current systems use DC
   current from an external power supply.  The
   anodes are inert, do not corrode away, and do not
   require periodic replacement.

Chemical Indicators are leak detection methods that
   use test materials that produce a color change
   when exposed to a particular product.

Coatings  are corrosion  and chemical resistant
   materials that are sprayed, brushed, or rolled onto
   the metal surface  of a storage tank.  Coatings
   serve one of two main purposes: (1) they protect
   the metal from attack by a corrosive  liquid or
   environment, or (2) they protect  the product from
   contamination by corrosion products.

Continuous monitoring systems are leak detection
   systems that provide automatic, unattended leak
   monitoring over extended periods of time.   The
   sampling frequency typically involves  multiple
   measurements per  hour.

Control box life is the anticipated usable time period
   for the control box of a leak detection system.

Corrosion is the degradation of a material by its
   environment.  In the context of this report,  most
                                               G-1

-------
   corrosion is  electrochemical.  (See corrosion
   cell.)

Corrosion cell, also called an electrochemical cell,
   consists of (1) a metallic anode where oxidation of
   metal to  positive ions occurs; these positive ions
   detach from the metal entering the electrolyte,
   and this results in metal loss; (2) a cathode where
   reduction reactions consume the electrons
   generated by the oxidation reaction at the anode;
   (3) an electrical conductor between the anode and
   cathode; and (4)  an electrolyte wetting both anode
   and cathode.  All of these  components must be
   present for corrosion of buried structures to occur.

Costs refer to the price of purchasing,  installing, and
   maintaining a leak detection system.

Data  capture is the percentage of valid measure-
   ments retained.

Detection  limit  is the  minimum  amount  or
   concentration of  a substance (pollutant) that can
   be identified, measured,  and reported with 99
   percent confidence that the analyte concentration
   is greater than zero.  It is  determined  from
   analysis  of a sample in a given matrix containing
   the analyte.

Dielectric constant  is a value that serves as an index
   of the  ability of a  substance to resist the
   transmission of  an electrostatic force from one
   charged body to  another.  The lower the value, the
   greater the resistance.

Double-wall pipe refers to two pipes  in one (i.e., a
   complete pipe enclosed within a secondary pipe).
   These are typically provided with a means  for
    monitoring the space between the inner and outer
    pipes for a leak in either pipe.

Double-wall tank refers  to two tanks  in one (i.e., a
    complete tank enclosed within a secondary tank).
    These are typically provided with a means  for
    monitoring the space between the outer and inner
    tanks (called the annulus) for a leak in either tank.

Drift is the change in baseline readings with time
    because of internal electronic variations.

Electrolyte is any  medium containing mobile ions
    which can conduct a current.   Soil moisture and
    groundwaters are the electrolytes of concern with
    buried underground tanks.

Electrolytic corrosion  (see also stray current
    corrosion)  is electrochemical corrosion as a
    result of impressed electrical currents from
   sources other than the intended circuit.  These
   "stray currents" impress a negative potential,
   relative to the electrolyte, on some areas of the
   affected structure.  These areas are cathodically
   protected.  Other areas develop impressed
   positive (anodic) potentials, become anodes, and
   suffer accelerated corrosion.  Sources of stray
   currents may be cathodic protection  systems of
   surrounding facilities, factories or shops using DC
   current equipment  (i.e., arch welders), electrified
   railways or transit systems, and buried  utility
   power cables. Improper grounding of electric
   equipment connected to the buried structure may
   also cause stray current corrosion.

Electrical Insulation  is a material which does not
   conduct electrons.  Placing an electric insulator
   between two  dissimilar  metals will prevent
   galvanic corrosion.

Electrical resistivity sensors are leak detection
   cables that deteriorate  in the presence of
   petroleum product.  This  causes a change in an
   electrical signal, thereby activating an alarm.

EMSL  (Environmental Monitoring  Systems
   Laboratory) is the part of the U.S. Environmental
   Protection Agency  responsible for developing the
   technical background necessary  for developing
   regulations for leak monitoring.

Fall time is the time required  for the detector to return
   to a near-baseline reading after the pollutant is no
   longer present.

FRP (fiber-reinforced plastic) is a composite
   material made up of a resin (typically epoxy or
   polyester)  reinforced with fibers.  Spun glass in
   strands or woven mats  is the usual  reinforcing
    material.      FRP   does  not   corrode  by
    electrochemical process  and is unaffected by
   groundwater.   FRP is widely used for corrosion-
    resistant pipe and tanks. It can  be  severely
    degraded  by some commercial products which
    may be stored in underground storage tanks.

Galvanic corrosion occurs  when dissimilar metals,
    such as steel and brass, are electrically connected
    together and are  placed in the soil  electrolyte.
    One of the two  metals, steel in the above
    example, becomes an anode and corrodes at an
    accelerated rate, especially when  it is adjacent to
    the other metal.   Galvanic  corrosion can be
    prevented by using special isolation fittings to
    join the two materials.

Geotextile is  a textile fabric,  such as a filter fabric
    used in civil engineering applications.  It is used in
                                                 G-2

-------
    conjunction with  synthetic  liners to provide
    structural support.

Grab sampling is the collection of discrete soil, water,
    or gas samples from a given area for analysis.

Ground water is the water beneath the ground surface
    that fills the cracks and pore spaces of rocks or
    soils.

Groundwater masking occurs when a leak is present
    but is not detected by integrity testing because the
    hydrostatic  pressure outside the tank equals  the
    head pressure inside the tank, and no net fluid
    level changes occur.

Henry's Law states that the amount of  a gas that
    dissolves in a given quantity of a liquid at constant
    temperature is directly proportional  to the partial
    pressure of the gas above the solution.

Henry's Law constant is the compound-specific
    proportionality constant in Henry's Law equations.

Inclined tank refers to an underground storage tank
    that is not level.   Therefore, the manufacturer's
    product level versus tank volume charts are  not
    accurate.

Instrument response time is the time required for the
    instrument  to register 95 percent of the final
    reading (true value) once the  detector comes in
    contact with the substance of interest.

Integrity testing refers to in-tank procedures used to
    determine if an underground storage tank system
    is leaking.  These tests typically involve shutting
    down the facility for up to a day and temporarily
    installing specialized test equipment.   They
    provide a point-in-time determination of whether
    the system is leaking.

Interface probes are leak detectors that utilize both
    fiber optics to identify liquid levels in a monitoring
    well and conductivity probes to  differentiate
    between oil and water.

Interferences are  any chemical  substances  or
    physical  phenomena that hinder the performance
    of the leak detection system.

Interior liner is a corrosion and chemical resistant
    material which is sprayed, brushed,  or applied
    onto the  interior of a tank.  This protects the  metal
    from attack from corrosive  liquids or environments
    and protects the  product from contamination by
    corrosion products.
Intermittent  monitoring systems refers to  the
    manual, periodic sampling of observation wells for
    leak detection.

Interstitial monitor refers to a leak detector used in
    the annular space of a double-walled tank or pipe.

Intrinsic safety is the ability of monitoring a device to
    operate safely in  recommended operating
    environments.  Also,  it is the acceptability of  any
    safety-related information printed on the device
    and in the operating manual.

Inventory control refers to measurements and record
    keeping designed to track all transfers of product
    into and out of a storage tank.  An imbalance or
    discrepancy between measured levels and  the
    delivery and use receipts may indicate that a leak
    is present.

Isolation fitting is  a device for connecting pipes of
    dissimilar  metals together without an electrical
    connection, and thus, for preventing galvanic
    corrosion.  For smaller pipe sizes, the device
    consists of a specially designed "isolation union"
    with  an insulator insert.   Special gaskets  are
    available for flanged connections. Great care is
    required to be  sure that there  is no alternate
    conductor  path around the isolation fitting, or no
    benefit will occur from its use.

Lag time and rise time when summed are the total
    length of time for an alarm to be activated once
    the sensor comes in contact with the analyte at a
    level above the detection limit.   For electronic
    devices, lag time is the time for a discernible
    signal to be generated once the monitor comes in
    contact with the specie of interest.  Rise time is
    the  time from  when a discernible  signal is
    generated until an alarm level (or 95 percent of the
    final reading) is reached.

Leak detection  refers  to any  approach used to
    determine  whether an underground tank is tight
    (not leaking); it includes integrity testing, inventory
    control, and leak monitoring.

Leak monitoring refers to the examination of the area
    outside the tank for evidence of free product.

Liner refers  to synthetic or natural  (e.g.,  clay)
    materials used to cover the bottom and sides of
    the excavation pit to serve as secondary or tertiary
    containment.

Llthology is the character of a rock formation.
                                                G-3

-------
LUST (Leaking Underground Storage Tanks) is an
   acronym frequently used as a catch-all term to
   describe topics related to underground storage
   tanks.

Maintenance schedule is the frequency of inspection
   and repair required to maintain reliable system
   performance.

Monitoring  refers  to all  procedures used to
   systematically inspect and collect data on
   operational parameters.

Monitoring well is a well that extends from surface
   grade  to several  feet below the water table (or
   several feet below the tank bottom in arid areas)
   and that permits leak detection devices to sense
   the subsurface environment.

Noise  refers  to  any background  or   signal
   interferences.

Operating environment is the range of environmental
   and operating conditions (e.g., temperature, pH,
   line voltage) that a leak monitoring device will
   experience during its usable life.

OUST (Office of Underground  Storage Tanks) is
   the part of the U.S. Environmental Protection
   Agency established to oversee the regulatory
    effort for underground storage  tanks.

Overfill protection refers to the use of liquid level
    alarms or automatic shut-off valves to  prevent
    excess product from being delivered to a tank; as
    well as to impermeable  barriers, sorbents, and
    special couplings designed to  minimize and
    contain spilled product at transfer areas.

Permeability is the capacity of a porous medium to
    conduct or transmit fluids.

Pitting is  a particularly damaging form of corrosion in
    which small areas of the metal surface corrode
    rapidly to form cavities or holes.  The overall
    corrosion rate may be low while penetration of the
    tank wall occurs rapidly  in a few isolated areas.
    Unprotected buried steel does pit rapidly under
    certain soil conditions.

 Porosity  is the ratio of the volume of interstices of a
    material to the volume of its mass.

 Precision is the measure of the ability to make
    replicate  measurements, i.e., an estimate of
    random error.
Product  refers  to  any  material stored  in  an
   underground  tank.  In this report, product  is
   typically assumed to be petroleum in some form,
   such as gasoline, fuel oil, or diesei fuel, etc.

Product permeable devices are leak detectors that
   allow volatile petroleum product vapors, but not
   water vapor, to pass through a coated surface to a
   sensing element.

Product soluble devices are  leak detectors that
   contain a polymer that dissolves  in petroleum
   product but not in water.  This dissolution can be
   used to trigger an alarm by any one of several
   designs.

Qualitative Integrity test is an integrity  test that
   determines if an underground storage tank system
    is leaking but that does not specify a leak rate.

Quantitative Integrity test is  an integrity test that
    determines whether  or not  an underground
    storage tank system is leaking and that provides a
    leak rate.

RCRA (Resource Conservation and Recovery Act)
    is  the law in which  Congress has  required
    regulation of  most underground storage tanks
    containing petroleum  products.

Recommended  operating environment is the
    vendor's estimated working  range for its  system
    with  regard to temperature, humidity,  etc. (see
    also operating environment).

Response time is the instrument response time plus
    the time for  any  leaked product to reach the
    sensor (see also instrument response time).

Sacrificial protection  is the  minimization  or
    prevention of corrosion of a metal in an electrolyte
    by galvanicaily coupling it to a more anodic metal
    that literally is consumed; hence, sacrificial.

Sampling frequency is  the  number of  sampling
    events per unit time.

 Secondary containment refers to a system installed
    so that  any volume of leaked  material from the
    primary containment is prevented from reaching
    the soil or water outside the containment  for  the
    anticipated period of time necessary to detect and
    recover the leaked material.

 Sensor life is the anticipated reliable time period for
    the sensing element  of a leak monitoring system.
                                                G-4

-------
Service life is the expected useful life of the control
   box, sensors, and ancillary equipment.

Sheen is an iridescent appearance on the surface of
   water.

Signal/noise is the ratio of a discernible measured
   value to the normal signal output when no sample
   is present.

Specificity is the ability of a monitor to detect  a
   specific chemical or class of chemicals.

Stray current corrosion is corrosion resulting from
   direct current flow-through paths other than the
   extended circuit.  Service stations, for example,
   built near cathodic protection rectifiers, factories or
   shops using DC, or  electrified (P.C.) railways or
   transit  systems  may experience  stray current
   corrosion.

Synthetic liner is a plastic or rubber sheeting used to
   line an excavated area.

Tank-end deflection refers to the outward movement
   of the ends of a steel storage tank when product  is
   added to the tank. The term may also be used to
   refer to the bowing out of the sides of a fiberglass
   tank after filling.

Thermal conductivity sensors are floating leak
   detection probes that measure heat loss at the air-
   liquid interface  in  a monitoring well.  They
   distinguish between air, water, and product.

Threshold detection is the lower limit  of detector
   sensitivity.
U-tube refers to a collection system for leaked product
   that can be used to underlie  a storage tank in
   areas with deep groundwater. The U-tube permits
   liquid-phase leak detection methods to be
   employed.

Underground storage tank (UST) systems refer to
   tanks  buried underground and to the related
   system  composed  of product lines, pumps,
   dispensers, and associated appurtenances for the
   storage and dispensing of  light  petroleum
   products. Any storage system  with 10 percent or
   more of its volume below ground is considered an
   UST system.

Vapor pockets are small volumes of volatilized
   product that may accumulate  against the upper
   surface of a tank and that may  affect integrity test
   results.

Vapor pressure is the pressure characteristic at any
   given temperature of a vapor in equilibrium with its
   liquid or solid form.

Viscosity  Is the property of a fluid that enables it to
   develop and maintain an amount of shearing
   stress  dependent on the velocity of flow and then
   to offer continued resistance to flow.

Water table refers  to a  layer beneath the ground
   where  the rocks or soil are saturated; it separates
   the phreatic zone (below) from the vadose zone
   (above).
                                                G-5

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