【国外标准】 Standard Practices for Electrical Methods for Mapping Leaks in Installed Geomembranes

4.1 Geomembranes are used as impermeable barriers to prevent liquids from leaking from landfills, ponds, and other containment facilities. The liquids may contain contaminants that, if released, can cause damage to the environment. 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, and punctures caused by traffic over rocks or debris on the geomembrane or in the subgrade.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 Electrical leak location methods are used to detect and locate leaks for repair. These practices can achieve a zero-leak condition at the conclusion of the survey(s). If any of the requirements for survey area preparation and testing procedures is not adhered to, then leaks could remain in the geomembrane after the survey. Not all of the survey area requirements are possible to achieve at some sites, but the closer the site can come to the ideal condition, the more successful the method will be.1.1 These practices describe standard procedures for using electrical methods to locate leaks in geomembranes covered with liquid or earthen materials, or both.1.2 These practices are intended to ensure that leak location surveys are performed to the highest technical capability of electrical methods, which should result in complete liquid containment (no leaks in 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, the method can still be performed, but any issues with site conditions are documented.1.4 Leak location surveys can be used on geomembranes installed in basins, ponds, tanks, ore and waste pads, landfill cells, landfill caps, and other containment facilities. 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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.6 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. A current limiter of no greater than 290 mA should be used for all direct current power sources used to conduct the survey.1.7 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.1.8 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.