Each month Tim Stark introduces a new technical topic for discussion and possible action. This month’s topic is: “Surface Repair of Thin Geomembranes”. This topic generated significant discussion with the main “take-aways” listed below:

 Geomembrane Thickness

-      Thin geomembranes are usually (< 30 mil thickness) for temporary and non-critical containment applications
-      Examples of thin geomembranes = Woven Coated Polyethylene (WCPE) & linear low density polyethylene (LLDPE)
-      Thin geomembranes can be welded in a factory but difficulties in field
-      Thin geomembranes are preferred to create large factory fabricated factory panels
-      IAGI CWT Program could be expanded to include thin geomembranes

Temporary Repair/Welding Techniques

-      Solid Wedge weld– 12 to 20 mil is possible for thin geomembranes
-      Hot air wedge weld – 12 to 20 mil is possible for thin geomembranes
-      Hot air gun –Patches – 12 to 20 mil is possible for thin geomembranes
-      Tapes –available but not preferred unless for cap strip over a patch
-      Available tapes– Tapecoat/Chase Adhesives is a tape and primer supplier
-      Tape may be stable for a temporary small patch until crew arrives to install proper patch
-      Tape is available single-sided and double-sided tape
-      Tape may be useful for underwater applications
-      Can use tape to help seal penetrations
-      Tape is not preferred for long-term applications
-      No good adhesive for polyethylene based materials
-      Do you require trial welds for patches? Not for heat guns
-      Need some documentation/guideline to improve quality of field welding thin geomembranes - ASTM D8468-23 Practice for Data Recording Procedure may be a useful reference

Repair Testing

-      Air lance testing is preferred – ASTM D4437
-      Vacuum box testing preferred but limited with WCPE geomembranes b/c air can pass through patch with a thin geomembrane
-      Electrical leak surveys can be used with thin geomembranes

CQA of Thin Geomembranes

-      Can field test seams in shear
-      Peel testing of seams is limited
-      Same seam test procedures as thick geomembranes including documentation
-      No warranty on patching old thin geomembranes – case by case determination – only warranty repair was made “with good workmanship