ASTM D8265-23

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Designation: D8265 − 21 D8265 − 23
Standard Practices for
Electrical Methods for Mapping Leaks in Installed
Geomembranes
This standard is issued under the fixed designation D8265; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 These practices describe standard procedures for using electrical methods to locate leaks in geomembranes covered with liquid
or earthen materials, or both.
1.2 These practices are intended to ensure that leak location surveys are performed to the highest technical capability of electrical
methods, which should result in complete liquid containment (no leaks in geomembrane).
1.3 Not all sites will be easily amenable to this method, but some preparation can be performed in order to enable this method
at nearly any site as outlined in Section 6. If ideal testing conditions cannot be achieved, the method can still be performed, but
any issues with site conditions are documented.
1.4 Leak location surveys can be used on geomembranes installed in basins, ponds, tanks, ore and waste pads, landfill cells, landfill
caps, and other containment facilities. The procedures are applicable for geomembranes made of materials such as polyethylene,
polypropylene, polyvinyl chloride, chlorosulfonated polyethylene, bituminous material, and other sufficiently electrically
insulating materials.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 The electrical methods used for geomembrane leak location should be attempted only by qualified and experienced personnel.
Appropriate safety measures should be taken to protect the leak location operators, as well as other people at the site. A current
limiter of no greater than 290 mA should be used for all direct current power sources used to conduct the survey.
1.7 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
These practices are under the jurisdiction of ASTM Committee D35 on Geosynthetics and are the direct responsibility of Subcommittee D35.10 on Geomembranes.
Current edition approved May 1, 2021Nov. 1, 2023. Published May 2021November 2023. Originally approved in 2019. Last previous edition approved in 20202021 as
D8265 – 20.D8265 – 21. DOI: 10.1520/D8265-21.10.1520/D8265-23.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8265 − 23
2. Referenced Documents
2.1 ASTM Standards:
D4439 Terminology for Geosynthetics
D7909 Guide for Placement of Intentional Leaks During Electrical Leak Location Surveys of Geomembranes
3. Terminology
3.1 For general definitions related to geosynthetics, see Terminology D4439.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 actual leak, n—for the purposes of this standard, the term “actual leak” is used for a leak to distinguish it from an artificial
leak.
3.2.2 anomaly, n—electrical measurement caused by some aberration in the survey area, which may or may not be a leak.
3.2.3 artificial leak, n—for the purposes of this standard, an artificial leak is an electrically insulated disk with a circular
conductive electrode, which electrically mimics a leak in the lining system and is used to confirm method functionality without
creating an actual leak in the lining system.
3.2.4 conductive-backed geomembrane, n—a specialty geomembrane manufactured using co-extrusion technology featuring an
insulating layer in intimate contact with a conductive layer.
3.2.5 current source electrode, n—the electrode that is placed in the water or earthen material above the geomembrane.
3.2.6 dipole measurement, n—an electrical measurement made on or in a partially conductive material using two closely spaced
electrodes.
3.2.7 earthen material, n—sand, gravel, clay, silt, combinations of these materials, and similar materials.
3.2.8 electrically isolated conductive-backed geomembrane installation, n—an installation of conductive-backed geomembrane
that achieves a continuously conductive surface on the bottom layer while electrically isolating the bottom conductive layer from
the top insulating layer of the entire geomembrane installation.
3.2.9 known leak, n—for the purposes of this standard, a known leak is a circular hole in the geomembrane intentionally placed
by the owner or owner’s representative per Guide D7909.
3.2.10 leak, n—for the purposes of this standard, a leak is any opening, perforation, breach, slit, tear, puncture, crack, or seam
breach in the lining system. Liquid must flow through a leak. Scratches, gouges, dents, or other aberrations that do not completely
penetrate the geomembrane are not considered to be leaks. Types of leaks detected during surveys include but are not limited to:
burns, circular holes, linear cuts, seam defects, tears, punctures, and material defects.
3.2.11 potential, n—electrical voltage measured relative to a reference point.
3.2.12 primary geomembrane, n—the uppermost geomembrane in a lining system containing multiple geomembranes.
3.2.13 site response current, n—the value of current, typically expressed in milliamps, resulting from applying a voltage to a
current source electrode inserted into the material covering the geomembrane in the survey area with the current return electrode
connected to the underlying conductive layer.
3.2.14 survey, n—for the purposes of this standard, a survey is an electrical evaluation of a geomembrane-lined containment
facility to check for leaks in the geomembrane.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
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3.2.15 survey area, n—the portion of the geomembrane-lined containment facility subjected to an electrical leak location survey.
4. Significance and Use
4.1 Geomembranes are used as impermeable barriers to prevent liquids from leaking from landfills, ponds, and other containment
facilities. The liquids may contain contaminants that, if released, can cause damage to the environment. Leaking liquids can erode
the subgrade, causing further damage. Leakage can result in product loss or otherwise prevent the installation from performing its
intended containment purpose. For these reasons, it is desirable that the geomembrane have as little leakage as practical.
4.2 Geomembrane leaks can be caused by poor quality of the subgrade, poor quality of the material placed on the geomembrane,
accidents, poor workmanship, manufacturing defects, and carelessness.
4.3 The most significant causes of leaks in geomembranes that are covered with only water are related to construction activities,
including pumps and equipment placed on the geomembrane, accidental punctures, and punctures caused by traffic over rocks or
debris on the geomembrane or in the subgrade.
4.4 The most significant cause of leaks in geomembranes covered with earthen materials is construction damage caused by
machinery that occurs while placing the earthen material on the geomembrane. Such damage also can breach additional layers of
the lining system such as geosynthetic clay liners.
4.5 Electrical leak location methods are used to detect and locate leaks for repair. These practices can achieve a zero-leak condition
at the conclusion of the survey(s). If any of the requirements for survey area preparation and testing procedures is not adhered to,
then leaks could remain in the geomembrane after the survey. Not all of the survey area requirements are possible to achieve at
some sites, but the closer the site can come to the ideal condition, the more successful the method will be.
5. Summary of the Electrical Leak Location Methods
5.1 One output of an electrical excitation power supply is connected to a current source electrode placed in the material covering
the geomembrane. The other output of the power supply is connected to an electrode in contact with electrically conductive
material under the geomembrane. This creates a voltage differential between the material over the geomembrane and the material
under the geomembrane.
5.2 When there are leaks in the geomembrane, electrical current flows through the leaks, which produces high current density and
a localized anomaly in the voltage potential distribution in the material above the geomembrane. Electrical measurements are made
to locate those areas of high current density corresponding to the presence of leaks.
5.3 Direct current and alternating current excitation power supplies and potential measurement systems have been used for leak
location surveys.
5.4 Various types of probes can be used to perform the surveys. Some are for placement upon earthen materials, some are for when
the operator wades in water, some are for towing the probe back and forth across a filled pond, and some are for raising and
lowering along vertical walls of a tank.
5.5 Measurements are typically made along parallel survey lines or in a grid pattern. They are recorded and then organized into
an electrical map of the survey area.
5.6 Electrical measurements must be made as close to the geomembrane as possible. The thickness of earthen cover materials,
including impenetrable sludge or concrete, should be minimized and should not exceed approximately 3 m, though this thickness
limit is highly site specific and a thicker cover material will reduce sensitivity while not necessarily causing the survey to be
ineffective.
5.7 An electrical map created from the electrical measurements is adjusted in order to clearly display a characteristic leak signal,
and the survey area is analyzed for the presence of any signals characteristic of a leak.
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5.8 The approximate location of a leak signal is determined from the electrical map, and additional measurements are typically
made in the vicinity of the detected leak signal to more accurately determine the position of the leak, if possible.
5.9 The leak detection sensitivity depends primarily on the survey area conditions. Optimal survey area conditions are described
in Section 6. The leak detection sensitivity is also a function of the conductivity of the materials within, above, and below the leak,
the electrical homogeneity of the material above the leak, the design of the measurement electrodes, the output level of the
excitation power supply, the detector electronics, the distance away from the leak during measurement, the survey procedures, the
presence of other leaks in the survey area, and data interpretation methods and expertise.
5.10 The survey rate depends primarily on the spacing between the measurement points, the type of data acquisition, the ease of
contact with the cover material, and the method of data analysis and time required for leak pinpointing.
5.11 One intent of these practices is to produce documentation of a zero-leak condition, so multiple surveys may be required if
leaks are found during the initial survey. For survey areas with leaks found during the first survey, a second survey may not be
necessary, especially if documentation of a zero-leak condition is not required. Current will flow preferentially through the largest
leaks in an impoundment and sometimes the smallest leaks will not draw current until the larger damage locations have been
repaired. The results of the initial survey should inform whether a second survey would be beneficial. It is possible that multiple
surveys will be required if the damage to the geomembrane is extensive.
5.12 In some impoundments, damage can be so extensive that the geomembrane fails to restrict current flow to discrete and
detectable leak locations. This can also be the case for sites that are not properly prepared for a survey. In these cases, electrical
methods may not be effective in locating the leaks.
5.13 Installed geomembranes vary in their ability to restrict current flow as a function of their bulk electrical resistivity, thickness,
contact with cover and subgrade materials, the surface area subjected to the applied voltage differential, and the impoundment
facility liner cross section. Quantification of current flow is used in these practices as a site-specific and condition-specific index.
6. Leak Location Survey Area Requirements
6.1 Sufficiently electrically conductive material must be present over the geomembrane, for example, earthen material or liquid.
Frozen earthen materials are not sufficiently electrically conductive. In the case of bare geomembrane, the survey area can be
flooded with water in order to perform this test method. The geomembrane should be subjected to a hydraulic gradient across the
geomembrane so that if a hole or breach exists in the geomembrane, it will leak either shortly before or during the testing. The
material covering the geomembrane should be as homogenous as possible. Anomalous features such as trenches or pipes are
allowed, but may produce anomalous electrical readings.
6.2 The material covering the geomembrane must be completely isolated from the material underneath the geomembrane. This is
typically achieved through an isolation trench around the entire perimeter of the survey area. It can also be achieved by a welded
flap of geomembrane that separates the cover material inside the survey area from the material outside, or the geomembrane
extending through the anchor trench to protrude above the earthen materials. Any conductive paths such as metal pipe penetrations,
pump grounds, and batten strips on concrete must be isolated or insulated from the water or earthen material over the
geomembrane. The only path for electrical current flow must be through leaks in the geomembrane under the level of water or
earthen materials covering the geomembrane in the survey area.
6.3 There must be a sufficiently conductive material directly below the electrically insulative geomembrane being tested.
Typically, leak location surveys on a properly prepared subgrade will have sufficient conductivity. Under proper conditions and
preparations, geosynthetic clay liners (GCLs) can be adequate as conductive material. There are some conductive geotextiles or
other conductive materials with successful field experience which can be installed beneath the geomembrane to facilitate electrical
leak location surveys on geomembranes without an underlying conductive layer.
6.4 For lining systems comprised of two geomembranes with only an electrically insulative geonet or a geocomposite between
them, the volume between the geomembranes can be filled with water to create an electrically conductive layer. The water level
in the
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