Locating Geomembrane Liner Leaks under Waste in a Landfill

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Abstract
An Electrical Leak Imaging and Monitoring (ELIM SM) survey was used to locate leaks under 2.5 meters of stabilized waste in an active geomembrane-Iined landfill. The landfill is lined with two 2-mm thick HDPE geomembranes that are separated by a geonet drainage layer. The primary liner is covered with 600 mm of drainage sand and 2.5 meters of stabilized waste for a total cover thickness of more than 3 meters. The principle of the ELIM method is to apply a voltage across the geomembrane liner and then to measure the resultant electrical potentials at widely spaced points. The data is processed using specialized mathematical inversion algorithms to image the locations of the leaks. The processed data indicated a leak near the center edge of the landfill cell. The suspect area was excavated to reveal two 80-mm long cuts in the primary liner.

Introduction
A high-voltage electrical leak location survey method has been used to locate leaks at more than 400 geomembrane-lined facilities world-wide (Laine and Darilek, 1993; Colucci et al., 1996). This commercial, field-proven technology has located many leaks that were not previously detected using other test methods and inspections, or that were caused during the placement of the protective soil cover. The method and equipment can locate leaks after the protective soil cover is placed over the liner and is a very cost-effective way to check liner installation quality or quickly solve a leakage problem. However, these commercial surveys are conducted using closely-spaced measurements on the soil with less than 1 meter of soil and no waste on the liner. The ELIM method is an advanced extension of this basic method that was developed to allow leaks to be detected under a much deeper soil and waste cover. In addition, the ELIM method allows for collection of data on a much wider spacing, or around the perimeter of a landfill cell, eliminating the need to place numerous data collection electrodes in the landfill cell. The ELIM method can also be used as a monitoring system.

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