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Landfill Geomembrane CQA and
Minimizing Leakage
Wyoming Solid Waste and Recycling Association
2015 Annual Conference
August 26, 2015
Michael Heinstein, PE
Solid Waste Engineer
Solid Waste Professionals of Wyoming, LLC
Outline
• CQA Regulatory Refresher
• CQA Discussion
• Minimizing Landfill Leakage – CQA and Electrical Leak
Location Surveys
• Electrical Leak Location Methods
• Summary; Best Practices for Minimizing Landfill
Leakage
• Additional Issues for Discussion
CQA Regulatory Refresher
CQA refers to a set of procedures performed during the landfill construction
project to ensure the constructed project meets the following:
1. Wyoming Department of Environmental Quality (WDEQ) Solid Waste
Rules and Regulations; specifically, adequate testing and evaluation of
liners shall be certified by a professional engineer licensed in Wyoming
and experienced in liner installation
2. The Landfill’s CQA Plan
3. Engineer’s Design and Technical Specifications
4. Industry Standards [Geosynthetic Research Institute (GRI)
and American Society of Testing and Materials (ASTM)]
CQA Discussion
We need to recognize that landfill construction projects are often awarded
to:
• Low bid Manufacturer (i.e., liner materials)
• Low bid General Contractor
• Low bid Geosynthetics Installer
Therefore, it is important that the selection of the Engineering Firm
performing CQA for the project be based on qualifications, not necessarily
cost. Ultimately, this process usually results in cost savings (i.e., future
liability) to the Owner because the CQA Technicians, Manager and
Engineer take ownership of the cell construction; that is, they own it until
approved by WDEQ.
Electrical Liner Integrity Surveys (ELIS)
Another technology available to complement the CQA Program is known
as Electrical Liner Integrity Surveys. These electrical survey techniques are
widely embraced as the state-of-the-art methods for locating leaks in
installed geomembranes.
Technology developed in the 1980s by the USEPA and Southwest
Research Institute. First ASTM standards addressing methods were
published in 2003.
Electrical Liner Integrity Surveys are increasingly being specified by
environmental regulations but are also applied voluntarily by many landfill
owners as responsible environmental stewards; and to minimize
future liability.
CQA and Electrical Leak Location Surveys
Can CQA be replaced by electrical leak location surveys? NO!, Why?
• Electrical liner integrity surveys only find holes in place directly after time
of construction
• CQA provides holistic quality control (evaluates strengths and installation
quality of materials):
1. Subgrade quality
2. Soil density requirements
3. Geomembrane seam quality and strengths
4. Geomembrane installation practices
Combined, they provide assurance for long-term performance
of the landfill liner system and minimize liability for the Owner
Value of Electrical Leak Location Surveys
What does an electrical leak location survey offer the landfill Owner:
• Directly checks integrity of installed geomembrane
• Can be performed before or after cover soil placement
• Can evaluate up to 100% of installed geomembrane
• Is the state-of-the-art practice CQA method for locating leaks (many
States and Owners require these surveys)
• It is the last safety net; finds problems that are not found by any
other means
• Method is quick and economical to perform
Value of Electrical Leak Location Surveys,
Continued
Evaluation of the origin of geomembrane holes and damage:
Even with a robust CQA program, approximately 75% of the damage to
the geomembrane occurs as the soil cover is placed; whereas, 25% is
associated to installation procedures. Of the 25% geomembrane
installation leaks, approximately 65% occur at extrusion welds at “T” and
“Y” joints; and approximately 20% of the geomembrane damage is due to
over-heating and melt-throughs. As a result, as a CQA Engineer, I always
require that these “T” and “Y” joints are extrusion welded as typically is
done; however, I require an additional “patch” extrusion welded over the
welded joints.
It is therefore imperative that during the design phase of the
liner panel layout, engineers need to minimize the need for
excessive extrusion welding.
Electrical Leak Location Survey Methods
1. Exposed geomembrane methods:
• Water Puddle Method (ASTM D7002)
• Water Lance Method (ASTM D7703)
• Arc Testing Method (ASTM D7953)
• Spark Testing Method (ASTM D7240)
2. Covered geomembrane methods:
• Covered with water (ASTM D7007)
• Covered with soil, gravel, concrete, or other earthen materials
(ASTM D7007)
Exposed Geomembrane Methods
Water Puddle and Water Lance Methods:
Water is sprayed onto the geomembrane, creating an electrically
conductive layer above the geomembrane. A low voltage DC power
source is applied to the water above the geomembrane and grounded
to the earth below the geomembrane. The leak detection equipment
features an ammeter in series with the applied potential current. The
ammeter will register an increase in current in the presence of a leak,
resulting in an audible tone. The expected minimum sensitivity of these
Methods is a one (1) millimeter diameter leak.
Water Puddle Method
Water Lance Method
Exposed Geomembrane Methods
Arc and Spark Testing Methods:
These methods do not require the use of water.
For Arc Testing, a low voltage is introduced above the geomembrane and
grounded to the conductive layer below it. In the presence of a hole, an
electrical arc is formed along with an audible alarm. Since the arc testing
method is not dependent on water making good contact through the leak,
this method is more sensitive than the water-based methods.
For the Spark Testing method, a geomembrane with a conductive backing is
required; and a high DC voltage is introduced across the geomembrane,
creating a spark where there is a leak.
Sensitivity of these methods is a pinhole leak.
Exposed Geomembrane Methods
Spark Testing, Continued:
The spark test method is also used for the evaluation of on-site fabricated
pipe boots. In this case, a wire is placed between the seams prior to
extrusion welding. After welding, a high DC Voltage wand is used and if a
leak is present, a spark will arc between the wand and the embedded wire.
Exposed Geomembrane Methods
Arc Testing Method
Spark Testing Method
Covered Geomembrane Method
The principle of this leak detection method on a soil or water covered
geomembrane is to apply a voltage across the liner. Voltage is applied to an
electrode in the soil or water covering the geomembrane and to another
electrode in a conductive material below the geomembrane. Since the
geomembrane acts as an insulator, the applied voltage produces a uniform
electrical potential distribution in the material above the geomembrane when
no leaks are present. If a leak is present, the electrical current will flow
through the leak, which produces a high current density and a localized
abnormality in the material above the geomembrane. Electrical
measurements are made using a dipole survey probe or scissor action water
survey probe. A monitoring meter will produce an audible signal that increases
in intensity when approaching a leak. Typical sensitivity: ¼-inch diameter leak
under 2 foot cover soil; 1/16-inch diameter leak in water-covered area.
Covered Geomembrane Method
Soil-Covered Dipole Method
Soil-Covered Dipole Method
Water-Covered Dipole Method
Electrical Leak Location Survey Method
Selection
• Refer to ASTM D6747, “Standard Guide for Selection of Techniques for Electrical Detection of Leaks in Geomembranes”
• Selection will depend on desired sensitivity (smallest detectable hole), whether the geomembrane is exposed or covered, and how critical containment is
• If geomembrane is to be covered, the survey should always be done after cover material placement to locate most significant damage, but can also be done after geomembrane installation (while exposed) to locate smallest leaks
Summary; Best Practices for Minimizing
Landfill Leakage
• Possible but very improbable of installing geomembrane without
leaks; it makes no sense to install a geomembrane without checking
for leaks for a fraction of the installation cost (i.e., installation cost ~
$28,000/acre; Electrical Leak Location Survey cost ~ $2,000/acre)
• It costs (much) more to remediate an excessive leakage or failure
situation than to do it right the first time
• As a minimum, soil-covered dipole method should be performed for
landfill cell construction to find significant damage
• For additional protection, an exposed geomembrane survey can be
performed immediately after geomembrane installation
• For very low (or no) leakage, conductive-backed
geomembrane should be used in tandem with Electrical Leak
Location methods before and after cover material placement
Additional Issues for Discussion
• Landfill Cell Engineering Design: Engineers need to design proposed
cells as simply as possible. Examples include leachate collection sumps
and leachate collection trenches where leachate is generally
concentrated (i.e., minimize the number of seams especially extrusion
welded seams)
• Double liners cannot be electrical leak tested unless a conductive layer
is installed between the geomembranes; this is especially a concern in
double-lined sumps
• Geomembrane wrinkles; not only do they present poor contact between
the GCL/CCL having an impact on the shear strength (i.e., slope
stability), but also present a problem performing an Electrical Leak
Location Survey. Leak location can be accomplished but a
geomembrane with a conductive backing must be used, thereby
increasing liner capital cost by approximately 10 cents per square
foot ($4,356/acre).
Thank you and for more information
please contact the following people
• Bill Hensley
Solid Waste Professionals of Wyoming
307.462.4961
• Michael Heinstein, PE
Solid Waste Professionals of Wyoming
307.461.1577
• Abigail Beck, PE
TRI Environmental
512.623.0511
