【国外标准】 Standard Practices for Permanent Monitoring Systems for Electrical Leak Detection and Location

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.1.1 These practices describe standard procedures for using electrical methods to locate leaks in geomembranes covered with liquid, earthen materials, waste, and/or any material deposited on the geomembrane.1.2 These practices are intended to ensure that permanent leak detection and location systems are effective, which can result in complete containment (no leaks in the geomembrane).1.3 Not all sites will be easily amenable to this method, but some preparation can be performed in order to enable this method at nearly any site as outlined in Section 6. If ideal testing conditions cannot be achieved (or designed out), the method can still be performed, but any issues with site conditions must be documented.1.4 Permanent monitoring systems for electrical leak detection and location can be used on geomembranes installed in basins, ponds, tanks, ore and waste pads, landfill cells, landfill caps, and other containment facilities including civil engineering structures. The procedures are applicable for geomembranes made of materials such as polyethylene, polypropylene, polyvinyl chloride, chlorosulfonated polyethylene, bituminous material, and other sufficiently electrically insulating materials.1.5 Any permanent electrical monitoring system must detect the occurrence of a leak through the geomembrane, and it must last longer than the monitored geomembrane by nature of the concept. Therefore, all buried components and mechanical and electrical connections must be made of material either the same as the geomembrane, in case of sensors situated above geomembrane, or made from a material with a longer lifespan in cases where they are situated under the monitored geomembrane.1.6 Permanent electrical monitoring systems are comprised of either large mesh pads separated by nominal spaces, or a grid of sensors situated either below the geomembrane or above the geomembrane or in both positions (below and above the geomembrane). In specific cases, sensors may be situated only at the perimeter of the monitored lined facility.1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.8 The electrical methods used for geomembrane leak location should be attempted only by qualified and experienced personnel. Appropriate safety measures should be taken to protect the leak location operators, as well as other people at the site.1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.10 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.