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Q: We are currently investigating a failure in a single composite liner system, caused by a settlement crack resulting from differential movement between the clay barrier and the underlying rock subgrade. This led to a tear in the geomembrane and subsequent flow through the underdrain system. The affected area has been exposed and is undergoing repair.
Our immediate concern is the potential for similar issues elsewhere across the facility, which covers a very large area. We’re seeking guidance on technologies or techniques—such as thermal imaging, electrical leak location, or other scanning methods—that could help identify potential subsurface discontinuities or liner vulnerabilities without full exhumation/excavation. Is there anything you can recommend to assist us with this assessment?
A: The best thing that we know of for detecting settlement cracks resulting from differential movement is lidar attached to low flying rotary drones. This technology has been around for 10 years and gets better every time I see it. It works over very large areas and can be coupled with GPS, aerial photography, thermal imaging and even gas monitoring. I should caution you that the technology needs to be calibrated or at least verified on site before each run. In addition, I have seen lidar fouled by vegetation, but this shortcoming can be overcome by an experienced operator.
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