What are Coatings for Flexible Geomembranes?‍

- Discussion started with discussion of a spray applied  polyurea geomembrane used for a water reservoir in Castle Rock, Colorado
- Pat Elliott showed  photos of a failed polyurea spray-on geomembrane – the coating is still intact  below water but not above water
- 2011 polyurea was  degraded down to the underlying nonwoven geotextile
- Specified minimum  thickness was 80 mil
- Polyurea outbid a 45  mil thick polypropylene geomembrane that was proposed by CLI in 2011
- Hard to CQA 80 mil  thickness of a spray-on geomembrane – push stick rule in with soft geotextile  underlying it makes thickness be larger so accurate measurement is hard
- Easier to check  spray thickness on a concrete subgrade
- Should heat bond top  of nonwoven geotextile b/c filaments can stick above spray-on polyurea so  hard to determine its thickness
- Water is getting  under spray-on geomembrane via seepage through nonwoven geotextile causing  water bulges below the water line
- Spray-on geomembrane  only lasted only 5 – 6 years and losing water
- Some of the tan polyurea  is still visible where the spray was thicker and indicates significant  variability in the spray-on process
- City is now going to  expand reservoir and replace the polyurea geomembrane
- Polyurea did not break up into small chips; itdisintegrated into dust and blew away,  which means the polymer degraded due to UV exposure  
- Usually  a short-term coating, i.e., life-span of less than 10 years
- FGI  does not recommend a coating as the only containment barrier, i.e., use only  for details and penetrations
- Safety  is important because of spraying chemicals so airborne and chemicals can be  hazardous
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