I'm a civil engineer in Pennsylvania, USA looking for some input. We have an ongoing debate about whether or not to use a geomembrane to separate a stone filled trench from the subgrade. I think it's fine on the top and sides, my experience has shown that if put on the bottom, clogging will result much more quickly. If a bottom separation is needed, I think an aggregate filter should be designed.
What do you think?
clogged soaker
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84-1093879891
It's standard practice over here to use the geo-membrane all around the trench, but the filter medium (or stone backfill) used to fill the trench is specially selected to have a low or non-existent fines content, so clogging hasn't been an issue - at least, not on the jobs on which I've been involved.
If you have a well-draining sub-grade, then I can't see a problem with using a graded filter medium to line the bottom of the trench, and then just lining sides and top with the membrane, but I have to wonder where all this clogging material is originating: is this a leach field for a septic system?
Alternatively, if it's just a distributor drain, would a catch-pit structure at the head of the run be a valuable addition? I'm thinking of the extra labour element involved in placing the filter medium and then lining just the sides and top, as opposed to lining the whole trench.
If you have a well-draining sub-grade, then I can't see a problem with using a graded filter medium to line the bottom of the trench, and then just lining sides and top with the membrane, but I have to wonder where all this clogging material is originating: is this a leach field for a septic system?
Alternatively, if it's just a distributor drain, would a catch-pit structure at the head of the run be a valuable addition? I'm thinking of the extra labour element involved in placing the filter medium and then lining just the sides and top, as opposed to lining the whole trench.