Leak Detection in Geomembranes
The “dipole method”, depicted in the schema above, is a geoelectrical method for detecting leaks, splits and tears in geomembrane materials. The method presents an elegant problem to a potentially time-consuming quality control problem: how do we ensure that geomembranes installed on-site, often covering thousands of square meters and essential to a site’s environmental integrity, have no faults or leaks? The dipole method neatly solves this problem, not by painstaking visual inspection or hazardous random sampling, but by harnessing the electrical insulation properties of the geomembrane.
Groupe Alphard specialise in a range of leak localisation solutions
Firstly, a voltage (around 500V DC) is applied to soil or sand covering the geomembrane material through a positive electrode. Secondly, a grounding electrode is positioned outside of the test site. Once the electrodes are in place, electrical charge from the positive electrode will pass through any faults in the geomembrane material, completing the circuit with the ground electrode and generating an electrical signature identifiable by the leak detection technician. No leaks, no faults? The geomembrane’s insulating properties prevents the charge from the positive electrode reaching the grounding electrode and no electrical signature is found. Applying the dipole method alongside a variety of localisation techniques, technicians can find faults as small as 1mm in geomembrane materials up to 1 meter thick.
The dipole method is not the only geotechnical approach to leak detection – Groupe Alphard specialise in a range of leak localisation solutions, including the water puddle method (ASTM D7002) and the spark test method (ASTM D7240). But the dipole method remains the most effective method for identifying faults produced during the covering of the geomembrane. For more information on other leak detection services offered by Groupe Alphard, visit our geomembrane quality assurance page.