On Fri, 10 Jan 2003 21:50:28 +0000, Simon Avery wrote:

"nick dickenson" wrote:

Hello nick

According to some (not all) of the books
I've read about ponding, using normal liners in saturated
ground is a bad idea, and say the liner will rise to the
surface. Personally I've got my doubts about that, given
the weight of water above it, and that the water is the
same density above or below the liner.

nd Liners will rise in a pond due to the decomposition of
nd organic matter below the liner. As long as any organic
nd matter (ie dead leaves etc) are removed prior to the laying
nd down of the liner, then it shouldn't fill with gas and rise.

Ooh, that does make sense, and thank you for the first rational answer
to that question I've ever heard. The books specifically state water
pushing it up, but yours does have an element of plausibility about
it - although how much organic matter would be in the subsoil at the
bottom of a (non-raised) pond I'm not sure.

--
Simon Avery, Dartmoor, UK Ý http://www.digdilem.org/
The offending organic matter that causes the problem is usually the type
that falls into the hole once it is dug (ie fallen leaves and other plant
matter such as grass, bits of weeds etc etc) These should be cleaned prior
to the laying of the liner or they will decompose and release gasses in
the process. It is these gasses that cause the liner to rise. Therefore,
if you dig your pond in the Autumn and it is going to be a couple of weeks
or so before you lay the liner, make sure you clear out the dead leaves
completely before you lay the liner or you will run into problems.
I can't see how water could cause the liner to rise? I would have thought
that water would take the path of least resistance, so if your pond is in
the way it would surely track sideways and find another exit. Or maybe I'm
wrong, it has been a long time since I was last at school!! Also, I always
thought that water finds "its own level" and if that is the case you are
more in danger of the water wanting to get out of your pond rather than
water trying to find its way in :-)
Thank you for your kind comments above though.