ASTM D6747-02e1

Standard Guide for Selection of Techniques for Electrical Detection of Potential Leak Paths in Geomembrane

SCOPE
1.1 This standard guide is intended to assist individuals or groups in assessing different options available for locating potential leak paths in installed geomembranes through the use of electrical methods. For clarity, this document uses the term potential leak path to mean holes, punctures, tears, knife cuts, seam defects, cracks and similar breaches over the partial or entire area of an installed geomembrane.
1.2 This guide does not cover systems that are restricted to seam testing only, nor does it cover systems that may detect leaks non-electrically. It does not cover systems that only detect the presence, but not the location of leaks.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory requirements prior to use.

General Information

• Status: Historical
• Publication Date: 09-Jan-2002
• ICS: 59.080.70 - Geotextiles
• Technical Committee: D35 - Geosynthetics
• Drafting Committee: D35.10 - Geomembranes

Relations

• Replaced By: ASTM D6747-04 - Standard Guide for Selection of Techniques for Electrical Detection of Potential Leak Paths in Geomembrane
• Effective Date: 01-Nov-2004
• Referred By: ASTM D7931/D7931M-21a - Standard Guide for Specifying Drainage Geocomposites
• Effective Date: 10-Jan-2002
• Referred By: ASTM D7007-16 - Standard Practices for Electrical Methods for Locating Leaks in Geomembranes Covered with Water or Earthen Materials
• Effective Date: 10-Jan-2002
• Referred By: ASTM D7953-20 - Standard Practice for Electrical Leak Location on Exposed Geomembranes Using the Arc Testing Method
• Effective Date: 10-Jan-2002
• Referred By: ASTM D7703-22 - Standard Practice for Electrical Leak Location on Exposed Geomembranes Using the Water Lance Method
• Effective Date: 10-Jan-2002
• Referred By: ASTM D7852-23 - Standard Practice for Use of an Electrically Conductive Geotextile for Leak Location Surveys
• Effective Date: 10-Jan-2002
• Referred By: ASTM D7909-21a - Standard Guide for Placement of Intentional Leaks During Electrical Leak Location Surveys of Geomembranes
• Effective Date: 10-Jan-2002
• Referred By: ASTM D6455-11(2018) - Standard Guide for the Selection of Test Methods for Prefabricated Bituminous Geomembranes (PBGMs)
• Effective Date: 10-Jan-2002
• Referred By: ASTM D7002-22 - Standard Practice for Electrical Leak Location on Exposed Geomembranes Using the Water Puddle Method
• Effective Date: 10-Jan-2002
• Referred By: ASTM D7240-18 - Standard Practice for Electrical Leak Location Using Geomembranes with an Insulating Layer in Intimate Contact with a Conductive Layer via Electrical Capacitance Technique (Conductive-Backed Geomembrane Spark Test)
• Effective Date: 10-Jan-2002
• Referred By: ASTM D7700-22 - Standard Guide for Selecting Test Methods for Geomembrane Seams
• Effective Date: 10-Jan-2002

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
e1
Designation:D6747–02
Standard Guide for
Selection of Techniques for Electrical Detection of Potential
Leak Paths in Geomembranes
This standard is issued under the fixed designation D 6747; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Editorial corrections were made in November 2002.
1. Scope 3.1.4 potential leak paths, n—for the purposes of this
document, a potential leak path is any unintended opening,
1.1 This standard guide is intended to assist individuals or
perforation, breach, slit, tear, puncture, crack, or seam breach.
groups in assessing different options available for locating
Scratches, gouges, dents, or other aberrations that do not
potential leak paths in installed geomembranes through the use
completely penetrate the geomembrane are not considered.
of electrical methods. For clarity, this document uses the term
Leakpathsdetectedduringsurveyshavebeengroupedintofive
potential leak path to mean holes, punctures, tears, knife cuts,
categories: (1) Holes—round shaped voids with downward or
seam defects, cracks and similar breaches over the partial or
upward protruding rims, (2) Tears—linear or areal voids with
entire area of an installed geomembrane.
irregular edge borders, (3) Linear cuts—linear voids with neat
1.2 This guide does not cover systems that are restricted to
close edges, (4) Seam defects—area of partial or total separa-
seam testing only, nor does it cover systems that may detect
tion between sheets, and (5) Burned through zones—areas
leaks non-electrically. It does not cover systems that only
where the polymer has been melted during the welding
detect the presence, but not the location of leaks.
process.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Significance and Use
responsibility of the user of this standard to establish appro-
4.1 Types of potential leak paths have been related to the
priate safety and health practices and determine the applica-
quality of the sub-grade material, quality of the cover material,
bility of regulatory requirements prior to use.
care in the cover material installation and quality of geomem-
2. Referenced Documents brane installation.
4.2 Experience demonstrates that geomembranes can have
2.1 ASTM Standards:
leaks caused during their installation and placement of mate-
D 4439 Terminology for Geosynthetics
rial(s) on the liner.
3. Terminology
4.3 The damage to a geomembrane can be detected using
electrical leak location systems. Such systems have been used
3.1 Definitions:
successfully to locate leak paths in electrically-insulating
3.1.1 electrical leak location, n—any method which uses
geomembranes such as polyethylene, polypropylene, polyvinyl
electrical current or electrical potential to detect and locate
chloride, chlorosulfonated polyethylene and bituminous
potential leak paths.
geomembranes installed in basins, ponds, tanks, ore and waste
3.1.2 geomembrane, n—an essentially impermeable mem-
pads, and landfill cells.
brane used with foundation, soil, rock, earth or any other
4.4 The principle behind these techniques is to place a
geotechnical engineering related material as an integral part of
voltage across a synthetic geomembrane liner and then locate
a manmade project, structure, or system.
areas where electrical current flows through discontinuities in
3.1.3 geosynthetic, n—a planar product manufactured from
the liner (as shown schematically in Fig. 1). Insulation must be
polymeric material used with soil, rock, earth, or other geo-
secured prior to a survey to prevent pipe penetrations, flange
technical engineering related material as an integral part of a
bolts, steel drains, and batten strips on concrete to conduct
manmade project, structure, or system.
electricity through the liner and mask potential leak paths. The
liner must act as an insulator across which an electrical
This guide is under the jurisdiction ofASTM Committee D35 on Geosynthetics
potential is applied. This electric detection method of locating
and is the direct responsibility of Subcommittee D35.10 on Geomembranes.
potential leak paths in a geomembrane can be performed on
Current edition approved Jan. 10, 2002. Published April 2002.
Annual Book of ASTM Standards, Vol 04.09.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D6747–02
FIG. 1 Schematic of Electrical Leak Detection Method
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D6747–02
exposed liners, on liners covered with water, or on liners volts DC. A hand-held probe is then traversed through the
covered by a protective soil layer, or both. water. An electrical current flows through the potential leak
paths causing localized abnormalties in the electrical paths as
5. Developed Systems
shownschematicallyinFig.3.Thetypicalprocedureistoflood
5.1 Electrical leak detection systems were developed in the
the test area, then locate the potential leak paths, drain the area
early1980’sandcommercialsurveyshavebeenavailablesince
and perform repairs. A hand-held probe or a probe on a long
1985. A short description of these systems is presented in this
cable is scanned through the water to locate these places where
section.
current is flowing through a leak. A typical procedure is to
5.2 The Water Puddle and Water Lance System—The tech-
flood the test area to a depth of approximately 0.15 to 0.75 m.
nique is appropriate to survey a dry uncovered geomembrane
This technique can locate very small leaks, smaller than 1 mm.
during its installation when placed directly on a subgrade that
The signal amplitude is proportional to the amount of electrical
is an electrically conductive layer below the geomembrane.
current flowing through the leak, so practical measures should
The lower conductive layer is usually the soil and the upper
be taken to maximize the current through the leaks. The signal
conductive layer being water. A cathode ground is established
amplitude is inversely related to the distance from the leak, so
and an anode is placed in a water puddle maintained by a
the scanning spatial frequency should be designed to provide
squeegee or to the water stream of a lance (as shown
the desired leak detection sensitivity.
schematically in Fig. 2). Water is usually supplied by gravity
5.3.1 Features—This system has the advantage of being
from a tank truck parked at a higher elevation than the lined
used to locate potential leak paths in in-service impoundments.
area. For this technique to be effective, the leaking water must
Primary and secondary liners can be tested. The water head on
come into contact with the electrical conducting medium to
the liner facilitates the survey speed by minimizing the
which the ground electrode of the 12 or 24 volts dc supply can
presence of wrinkles and waves, and lack of contact between
beconnected.Sincethegeomembraneisnotaperfectelectrical
the liner and the conductive soil at the bottom of slopes. This
insulator, a steady background signal can be audible. As the
technique can be used in wet conditions. The main advantage
water flows through a leak path, there is an increase in the
of this technique is the detection of leak paths with the
signal. Leak paths as small as 1 mm in size are then located by
protective granular layer covering the liner (after the installa-
an audio signal or by measuring a current of magnitude related
tionofthedrainagelayeronthegeomembrane)(referto5.5for
to the size of the leak. It can also be used to search for leak
description of the method). The survey rate depends primarily
paths in geomembrane-lined concrete and steel tanks.
on the spacing between sweeps and the depth of the water. A
5.2.1 Features—The main advantage of this system is the
close spacing between sweeps is needed to detect the smallest
possibility to detect leak paths in geomembrane joints and
leaks.The survey rate for a survey while wading, sweeping the
sheets as work progresses during the construction phase.
probe so that it comes within 0.25 m of every point on the
Larger leak paths do not mask smaller ones because this
submerged geomembrane is 800 to 1200 m /h per person. For
technique locates leak paths independently on uncovered liner.
2 a survey with a towed probe with the probe scanned within 0.4
The electrical survey rate of approximately 500 m /h per
m of every point, the survey rate is 800 to 1000 m /h per two
operator does not affect the installation work schedule and
persons, including establishing the survey lines. The approxi-
permits a rapid construction quality control (CQC) of the
mate setup time is 30 to 90 min.These times do not include the
installer work. The approximate setup time varies from 1 to 3
time to flood the liner.
h.
5.3.2 Limitations—The main disadvantage of this system is
5.2.2 Limitations—This technique cannot be used with a
that it cannot be applied to detect potential leak paths in
protective layer covering the liner. The presence of wrinkles
geomembrane joints and sheets as work progresses during the
and waves, steep slopes and lack of contact between the liner
construction phase since, because of the need to flood the
and the conductive soil at bottom of slopes inhibits the survey
geomembranewithwater.Thepresenceoflargeleakpathsmay
speed. This technique cannot be used during stormy weather
influence the detection of small leak paths in their vicinity.
when the membrane is installed on a desiccated subgrade, or
Depending on the bottom configuration of the surveyed appli-
wheneverconductivestructurescannotbeinsulatedorisolated.
cation, the water depth can be substantial in some areas; the
The procedure to detect potential leak paths in seams of repair
procedure is more lengthy consisting of flooding the area,
patches is difficult and lengthy since it requires a certain
probing to locate the leak paths and draining of the area to
infiltration time.
perform repairs.
5.3 The Water-Covered Geomembrane System—The prin-
ciple behind this system is to test the geomembrane while it is 5.4 The Electrically Conductive Geomembrane—
covered with water, a technique similar to the previous system Coextrusion technology makes possible the manufacture of a
requiringanelectricallyconductivelayerbelow(subgrade)and polyethylene geomembrane that can be spark tested. The
above the liner (water or saturated drainage layer). A cathode material has a thin layer of electrically conductive material as
ground is established and an anode is placed in contained an integral part of the geomembrane. This provides a way to
water.Thevoltageimpressedacrosstheliner(byahighvoltage spark test the installed geomembrane. The spark testing that
dc or ac power supply) produces a low current flow and a occurs in the field is very similar to the method used in the
relative uniform voltage distribution in the material above the factory to identify holes during geomembrane manufacturing.
geomembrane. To maximize this current, a high voltage power The conductive geomembrane is installed such that the con-
supply with safety circuits is used that can provide up to 400 ductive side is against the sub-base and the non-conductive
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D6747–02
FIG. 2 Schematic of Water Puddle and Lance Systems
side is on top.The testing utilizes a voltage source to charge an conductive element is then swept over the upper surface to
element such as an electrically conductive neoprene pad. The inspect for the presence of potential leak paths. Where a
charge is then transferred to the (underlying) conductive layer potential leak path occurs, a closed circuit is created and a
of the geomembrane through the capacitance effect. Another spark is produced as shown in Fig. 4. To facilitate leak path
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D6747–02
FIG. 3 Schematic of Water-Covered Geomembrane System
location, equipment must include an audible alarm. Different types of equipment are utilized depending on the area to be
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D6747–02
FIG. 4 Schematic of Conductive PE Geomembrane Leak Detection System
tested. For example, small, hand-held detectors are used in moisture, but it does not have to be saturated with water. It
confined areas and large detectors can be used on large, open requires an electrically conductive layer below the geomem-
areas. brane. The most common implementation of this method is to
5.4.1 Features—The main advantages of this technique are: make dipole measurements using two moving electrodes
this is the only system that utilizes a conductive grounding spaced a constant distance apart. Pole measurements can also
layer that is an integral part of the membrane being tested thus be made by making potential measurements on the protective
eliminating the issue of inconsistent grounding; it can be soil cover using one moving electrode referenced to a second
performed during construction; no water pumping is required; distant electrode. The data can be taken on a grid or at regular
current flow is miniscule; primary and secondary liners can be pointsalongparallelsurveylines.Thedatacanbeplottedinthe
tested; all slopes can be tested; it can detect leak paths smaller field and analyzed to locate areas with a characteristic leak
than 1 mm. The rate of testing depends on the type of signal. The data can be analyzed in raster data form or using
equipment used. Using a 2-m wide brush, travelling at 3 to 5 contour plots.
km/h, the rate can be up to 500–1,500 m /h. Repairs can be 5.5.1 Features—This method has the distinct advantage of
performed immediately upon location of a leak path.The setup locating potential leak paths that are made during the emplace-
time required is approximately 30 min. ment of the protective soil layer. These construction damage
5.4.2 Limitations—The presence of wrinkles and waves and leaks have been found to be prevalent type of damage to
steep slopes inhibits the survey speed. This technique cannot geomembranes that are difficult to detect during construction
be used during stormy weather. The location of leak paths with activities. This technique can be used in wet conditions. With
the protective granular layer covering the liner is not possible. proper signal sampling, this technique can locate small leaks,
It is not the intention of this method to replace traditional typically as small as 3 mm. The signal amplitude and distinct-
non-destructi
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