Stormwater detention pond

Geomembrane testing? Root penetration?
Welding HDPE with LLDPE? Woven geopipe?

Questions and answers from the GMA Techline

We are designing a campus that has a pond for stormwater detention, as well as an architectural/aesthetic pond that is about an acre in area, 6 feet deep, sideslopes 4H:1V, and is right up against a building.

The geotech engineer is suggesting that we provide a 20-mil LLDPE(S) geomembrane and cover it with a foot of soil. I talked to a couple of manufacturers and they suggested that we use at least 40-mil HDPE(S) for our scenario. What would be your suggestion based on your vast experience in the field?

Abner | USA

Abner,

The absolute thinnest material that I recommend is 0.63mm (0.25 mils) and that is for the “lowest” survivability ranking—20 mils is clearly not advisable.

Regarding thicker material, one can get 30 mils but even that is hard to properly weld so the recommended value of 40 mils is good advice from my point of view.

Bob Koerner | GMA Techline