Flammability? Zip ties? MARV? Ponds? GT specs?
Questions and answers from the GMA Techline.
I’m designing an effluent pond (the geotechnical aspect at least) and have a couple of questions:
- Do you see any issues with placing a gravel (rounded) subdrain system underneath the pond, sandwiched between a geomembrane (likely textured HDPE) and a geotextile (nonwoven, needle-punched) and placed directly on the compacted fill?
- For conservative estimates, do you have a ballpark geomembrane thickness for textured HDPE?
Tate | Montana
Gravel and geomembranes are not good bedfellows. There must be a nonwoven geotextile between them. The required weight is a design feature mainly dependent on the maximum height of liquid in the pond and the gravel type and size. Textured HDPE is certainly good for the sideslopes but sometimes I see smooth on the base.
Regarding thickness, there are three considerations: regulations, installation survivability, and technical. The latter is covered in the book Designing with Geosynthetics, sixth edition.
Lastly, people are constantly surprised by leakage rates in ponds. This is, of course, directly related to the head and conditions of both design and installation. We have a white paper on our website in this regard.
It might be helpful to consider an electrical leak integrity survey, offered by many firms.
Bob Koerner | GMA Techline