Why is air lance testing considered a non-destructive method for geomembrane liner QA/QC?

Air lance testing is considered a non-destructive method for geomembrane liner Quality Assurance/Quality Control (QA/QC) because it identifies defects without compromising the integrity or functionality of the geomembrane itself. The process involves directing a high-pressure stream of air onto the surface of the geomembrane seam. If there are pinholes, unbonded areas, or other imperfections in the seam, the high-pressure air will cause the geomembrane to deflect or blister, indicating a potential leak point. This deflection is visually observed by the inspector. Unlike destructive testing methods, such as cutting samples from the seam for laboratory testing, air lance testing allows for the entire seam length to be examined quickly and efficiently without requiring repairs or patches unless a defect is found. Because the air pressure is controlled and relatively low, it does not damage the intact portions of the geomembrane, making it a valuable tool for initial seam integrity assessment. If a defect is identified by air lance testing, then a repair is performed, and the repair area is retested. Therefore, the method allows for comprehensive seam inspection while preserving the geomembrane's overall barrier performance.