The
solution on the previous page will keep the water away and
allow you to dig out the hole. If you are building a pond
with a concrete base, and concrete walls then this would
keep out the water and so would not be a problem.
If you are using a liner then the water would only be kept out
of the excavation by the pressure of the pond water against the
liner. This would probably be OK as long as you did not need to
empty the pond, or pump out a large amount of the water. If you
did use this method then you would have to seriously consider ommitting
the bottom drain as under certain circumstances the outside water
could get under the liner and force it away from the securing screws.
Mark had considered putting in a concrete base which
would encase the bottom drains, but if you did not have
any block or concrete walls then the water could still
get between the liner and the concrete and disturb the
attachment to the bottom drain. Mark then had discussions with a koi dealer, and a builder
in his area and in the end it was decided that the best
solution to ensure that there was no problems in the
future that there should be a concrete base and that
the walls should be built up using 4ins thick concrete
blocks. Before doing this all the area of the pond would
be covered with a large double layer of polythene sheet
and the base and the walls would be contained inside
this so making this waterproof.
TIP.It
is always a good idea when you come up with a problem like
this to discuss it with a local builder or expert in their
field as they are aware of the local circumstances, and have
probably seen it all before.
Now
that it had been decided to put in a concrete base and use
concrete blocks for the walls the problem was what to do
about the concrete collar. Mark then decided to leave the
collar in place and to take away five inches of soil from
the walls so that he can use four inch thick blocks and have
one inch of cement behind.
The final solution can be seen in the two photos above. The base
has been dug down another 18 inches so that it is now six feet
deep below the intended water level. The concrete base will be
built up and benched so that the final pond is 5ft deep at the
sides and 5ft 4ins deep at the centre.
The weather has been fine whilst this extra work has been done
and so the water table has not been a problem.
The final words must come from Mark "If I was starting again
I would probably use blocks all through, but now the concrete
ring is in it a pity to waste it. What started out simple in
my mind has turned into something of an engineering job."
This website started with a
booklet which I made up originally for the help of those members of the BKKS
- South Wales Section who were intending to start building a koi pond, and as the website has expanded more information and articles from other people have been included. This
is for general guidance only, and we do not take any responsibility for problems
that might occur by following these ideas. It is important
that you check out everything in your area, and check on local laws and rules
that may apply.
