In message , Simon Avery
writes
"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.

Just to come back in here again, in my case there was no organic
material in the hole once the liner was removed - all there was was a
hole full of dirty brown water!
--
Steve Jackson