Standard Practices for Permanent Monitoring Systems for Electrical Leak Detection and Location

Importancia y uso:

4.1 Geomembranes are used as impermeable barriers to prevent liquids leaking out of landfills, ponds, and other containment facilities. In addition, geomembranes are also used to prevent external liquids leaking into to these types of facilities (for example, floating covers, landfill caps, and roofs of storage tanks). The liquids may contain contaminants that, if released, can cause damage to the environment or damage to the contents where protection is against leakage into the facility. In the case of a landfill cap, leakage increases the amount of leachate that the landfill can produce. Leaking liquids can erode the subgrade, causing further damage. Leakage can result in product loss or otherwise prevent the installation from performing its intended containment purpose. For these reasons, it is desirable that the geomembrane have as little leakage as practical.

4.2 Geomembrane leaks can be caused by poor quality of the subgrade, poor quality of the material placed on the geomembrane, accidents, poor workmanship, manufacturing defects, and carelessness.

4.3 The most significant causes of leaks in geomembranes that are covered with only water are related to construction activities, including pumps and equipment placed on the geomembrane, accidental punctures, punctures caused by traffic over rocks or debris on the geomembrane or in the subgrade, and ruptures caused by settlement during filling.

4.4 The most significant cause of leaks in geomembranes covered with earthen materials is construction damage caused by machinery that occurs while placing the earthen material on the geomembrane. Such damage also can breach additional layers of the lining system such as geosynthetic clay liners.

4.5 As a practical measure, other electrical leak location methods (see Guide D6747) should be used in conjunction with the permanent monitoring system to eliminate leaks in the installed geomembrane(s) as part of facility construction. Such methods must include testing of the exposed geomembrane before covering and before commissioning a permanent monitoring system. Then the permanent monitoring system can be used in conjunction with other cover geomembrane testing methods to quickly detect and locate all leaks caused by the covering process.

4.6 Permanent electric leak location monitoring methods are used to first detect and then subsequently locate leaks for repair during the whole life of the geomembrane. They are designed to detect and locate leaks at the end of the construction phase and during the operational and closure phases and also to monitor any post-closure phases. These practices can easily achieve a zero-leak condition at the conclusion of the measurement(s) at the end of the construction phase. If any of the requirements for measurement area preparation and testing procedures is not adhered to, however, then leaks can remain in the geomembrane after the construction phase completion measurement. On some sites it may not be practicable to achieve, but the closer the site can be designed (and carefully constructed to that design), the closer it will reach the ideal zero-leak condition.

4.7 Through the life of the facility monitored by an electric leak location system, leaks that are detected can be repaired. Often the difficulties of carrying out a repair are cited as a reason for not applying this method. However, history has shown that it may be better to know, in order to minimize late-life remedial work, by repairing leaks in a sector of a site rather than entirely exhuming and relocating (waste, for example) to a new site.

4.8 A permanent electric leak location monitoring system must last longer than the geomembrane it is designed to monitor, otherwise failure caused by degradation of that material will not be detected. To achieve this, all buried components and the associated electrical connections must be designed in such a way as to achieve this and additionally must avoid metallic corrosion of the buried components and/or critical connections.

Subcomité:

D35.10

Volúmen:

04.13

Número ICS:

21.140 (Seals, glands)

Palabras clave:

construction quality assurance; electrical leak location measurement; geoelectric leak location; geomembrane; leak detection; leak location; permanent monitoring system;