Electrical Leak Imaging and Monitoring (ELIM) System
From Leak Monitoring
In addition to manual leak location surveys, an Electrical Leak Imaging and Monitoring (ELIM) system can be permanently installed to monitor for leaks in the landfill liner. The ELIM system uses a series of electrodes placed on top of or underneath the geomembrane liner during liner installation. The electrodes are connected to an instrument panel used to make the electrical measurements. A data acquisition system collects and stores the data. The data is processed using advanced mathematical computer algorithms to calculate and display the positions of the leaks.
The electrical leak location method is a powerful tool used to detect electrical paths through leaks in a geomembrane liner. A voltage is applied to an electrode placed in the soil or water covering the liner and to an electrode placed in the leak detection zone for double-lined systems or connected to earth ground for single-lined systems. Because the geomembrane liner is an electrical insulator, current will flow only through leaks in the liner. This current produces localized anomalous areas of high current density near the leaks. Electrical measurements are then made on the soil or in the water to locate these points of current flow through the leaks. ASTM Standard Guide D-6747 describes the various implementations of the method. The electrical leak location method is suitable for liquid impoundments and tanks, as well as pre-service inspection of solid waste landfills. Electrical leak location surveys are conducted on the primary or secondary geomembrane liners with water or soil covering the liner. Surveys with soil on the liner are important to detect leaks caused by machinery used to emplace the soil cover. With proper site conditions and survey procedures, the electrical leak location method can detect and locate 0.001 square inch (0.6 square mm) leaks in liners covered with water and 0.04 square inch (26 square mm) leaks in liners covered with 2 feet (600mm) of soil.