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Temporary interim covers

Q&A: GMA Techline | April 1, 2024 | By:

Q: I am writing to inquire if you are aware of any recommendations or guidelines for removal of geosynthetic liners that have been used as temporary interim covers at landfills. We recommend facilities totally take up and remove the temporary cover; however, we have had some recent proposals to run over the liner with heavy equipment with the assumption that it will tear holes and damage the liner sufficiently. I still have concerns that the damage will not be adequate to prevent ponding or seeps and could cause potential instability in the waste if landfill operations are resumed in these areas. If you have any thoughts or are aware of any research or guidance on this topic, please let me know. 

A: We would strongly recommend totally taking up (i.e., removing) all the material from the temporary interim cover before construction of the final cover. This is supported by evidence from at least five case histories. In all five cases, the old interim cover created a partial barrier in localized spots and created a mess with mildew and trapped moisture. In addition to this partial barrier concern, the old interim barrier in three cases served as a weak shear interface with adjacent materials. This created both global and localized shear failure on a relatively shallow slope (less than 4:1). 

In addition, please consider recycling your temporary interim covers from the perspective of both benefit cost and sustainability. There are several companies specializing in this service. They recycle huge amounts of geomembrane liner from both depreciated landfill covers and surface impoundment. They can even handle geomembranes that are scrim reinforced. The process is entirely closed-loop, and accepts geomembranes after screening for contaminants. The “scrapers” clean and shred the material on-site, and then it is incorporated into commodity plastic used for non-critical applications or sold to the open market. I am awed by the diversity and scale of the market for used, reground and/or obsolete plastics. It is not only good for the environment but good business. Please note that like all materials, traceability is important and the durability of recycled plastics might be suspect.

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