Many modern landfill cells, lagoons, impoundments and ponds are lined with synthetic materials such as HDPE or PVC to prevent leakage. However, even with careful quality control during installation, many, if not most, liners have leaks - from imperfectly welded seams, or from stress on seams or punctures during installation of protective cover. Particularly for new landfill cells, leachate lagoons, or waste impoundments, rapid and accurate detection and pinpointing of leaks can prevent costly site closures, delayed permitting/opening, and (in the worst case) cleanup costs. Even for ponds containing benign materials such as irrigation or drinking water, leaks can cause costly site damage from washouts or sinkholes.
Enviroscan has developed a modified geoelectric leak detection method for locating leaks in any highly electrically resistive liner material. The principle is based on the simple idea that if a fluid can leak down through a hole in the liner, we can use strategically placed electrodes to force an electrical current to leak up through that hole. The exact electrode geometry depends on the construction details for the liner system. In general, single liners can be readily tested using the geoelectric method. In double-lined systems, only the upper (primary) liner can be tested geoelectrically, and then only if the detection or witness zone between the liners contains an electrically conductive (even very poorly conductive) material. Suitable materials in the detection zone include sand, gravel or any natural aggregate, geocomposite (containing clay), and damp woven or non-woven fabric. Synthetic grid is not electrically conductive, but a liner system with synthetic grid in the detection zone can still be tested if the detection zone is flooded. For liner systems with no protective cover, we have developed water jet electrodes that can be trained on seams or suspect areas to check for leaks. Leak detection through trash has been accomplished, but the likelihood of success is highly site-dependent. Leak detection through impounded electrically conductive materials such as leachate or brine is not generally possible, but can be successfully completed if the impoundment is drained.
Enviroscan can also detect leaks in most single liner systems and in the bottom or secondary liner in double-lined system by remotely measuring (using electromagnetic or EM methods) the moisture content of the soil or fill beneath the liner.
We have completed leak detection surveys on lined cells ranging in size from a few hundred square feet to hundreds of acres. Surface conditions have varied from bare liner, to gravel or soil cover, to flooded cells (surveyed from an inflatable dinghy). All surveys employ high accuracy global positioning system (GPS) location control to ensure precise documentation of liner conditions. In addition, as part of each survey, leaks are exposed for repairs as they are detected and pinpointed in order to eliminate later difficulties with relocation or reoccupation of potential leaks.