Like the water puddle method, the dipole method (standardized
by ASTM standard D7007) is a geoelectrical technique that
allows technicians to identify faults in the geomembrane
material made during installation. Again, the dipole method
uses the electrical insulation properties of the geomembrane
material to identify and locate faults.
However, whilst the water puddle method requires an external
water source to humidify the membrane surface, the dipole
method passes an electrical charge (around 500V DC) directly
into sand or soil material covering the geomembrane.
If any faults are present in the membrane, this charge will
pass through the fault to a grounding electrode placed in the
earth outside the test site, generating an electrical
signature identifiable by a qualified technician.
These faults can then be localised, providing a full profile
of the membrane’s material integrity. Groupe Alphard applies
the method as standardised by ASTM standard D7007.