Subdrain Trench Waterproofing

[palmahouse]

I am designing a subdrain and would like to call out for "waterproofing" on the downslope side. I have not designed one like it in quite some time. I used to call for 15-mil visqueen for this application, but, I would like some advice.

-Does the burried visqueen hold up over time? I ask this because I have seen some old visqueen below floor slabs that appeared to be deteriorated.

-Are there other commonly available (and cost effective) products that are worth considering that may be better? I figure I could call for STEGO vapor barrier (or an equivalent), but that may be too expensive for this small project.

 

[oldestguy]

I'd pose that question in the forum "Waste Disposal & Treatment".

These guys probably have experience in looking at what is inside landfills after many years. You hear stories about being able to read newspapers, or that plastics don't deteriorate. Perhaps they can relate what type of material they find doesn't deteriorate.

Landfill liner materials are a good possibility, since that stuff has to last.

 

[oldestguy]

While I an at it I might relate some information that I found when doing a Master's thesis for sub-drains under highways. I had soil moisture measurement devices (nuclear probes with a source of fast neutrons) that I inserted in tubes in roadways troubled by high water tables. Readings were taken at foot intervals in these tubes both before and after installing drainage.

I was able to see what effect happened by installing cut-off subdrains in these locations. Studies lasted 2 years by me and continued by others. Considerable time for readings before (for all seasons) and thereafter.

It was found that the down-hill water table dropped to an elevation no higher than the base of the trench, generally parallel to the original water table.

What this would tell me is that there is no need for any barrier in the subdrain trench, down-hill side.

Also learned was that on the up-hill side drawdown was generally rather ineffective in doing much. All sites had longitudinal or crossing grades between 3 and 10 percent. No attempt was made to do the studies in level ground.

 

[mehraneng]

If concrete is poured directly on top of Visqueen three things happen:
.The slab will have excessive curl

.Unless you use 10 mils or greater, the Visqueen will have many punctures

.Concrete placed directly on top of Visqueen will result in the degradation of the Visqueen due to the alkalinity
of the concrete

This is probably the reason that the visqueen got deterirated