The leakproof performance of containment sites is directly related to the material integrity of the geomembrane. Whilst Groupe Alphard’s quality assurances services ensure that only the highest quality geomembrane is delivered to site, installation and construction works present several threats to geomembrane integrity. Even the simplest of accidents during installation can cause faults that significantly impact a site’s economic and environmental performance. Leak detection therefore plays a key role in ensuring the continued operational viability of containment sites, and Groupe Alphard are industry leaders in a range of leak detection and localisation services.
Our leak detection professionals have over 15 years of experience in geoelectrical leak detection techniques. These techniques harness the electrical insulation properties of geomembrane materials, passing an electrical charge into the membrane and through possible faults to identify and localise leaks across the entire membrane surface. Groupe Alphard’s team continues to improve and refine these techniques, ensuring that our range of leak detection solutions keep up with the evolving demands of modern containment projects and innovations in geomembrane materials.
The water puddle method allows technicians to identify and locate potential leaks, faults or tears in a geomembrane occurring during installation. It applies a geoelectrical technique that harnesses the electrical insulation properties of geomembrane materials. A DC voltage is applied to metal roller that sprays water across the geomembrane service and a grounding electrode is placed in the earth outside of the test site, creating a difference in electrical potential between the roller and the underside of the membrane. If the roller passes over any faults sufficiently large for the water to leak through the circuit between the roller and the grounding electrode is completed, and a technician is notified by their detection equipment. As it only requires a thin layer of water to be applied gradually to the geomembrane, the water puddle method allows for technicians to perform tests with 100% coverage even on extreme slopes and uneven surfaces, with a resolution capable of identifying leaks and faults smaller than 1mm2. Groupe Alphard applies the method as standardised by ASTM standard D7002.
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.
Whilst the water puddle and dipole methods use geoelectrical techniques to identify faults in standard geomembranes, the spark test method allows technicians to identify leaks during the installation of a different form of conductive geomembranes. These conductive geomembranes are the result of recent innovations in geomembrane manufacturing methods, allowing a conductive layer to be included on one side of the traditional geomembrane layer. Technicians can also apply the spark test method to traditional geomembranes installed in direct contact with a conductive service.
To apply the spark test method, the geomembrane must be installed with the conductive layer facing downwards. A portable voltage source applies an electrical charge to the geomembrane which in turn acts as a capacitor, storing the electrical charge. When a metal brush is passed over the charged membrane, the stored electrical charge is released through any faults in the membrane as an electrical arc. This release is detectable by a technician and a single test pass over a conductive membrane gives leak detection technicians an accurate picture of its integrity, identifying faults, splits and tears as small as 1mm2. Groupe Alphard applies the method as standardised by ASTM standard D7240-06.