"'Mike'" wrote ...
"Graham99" wrote in message

Because the grass wouldn't grow very well in a part of my back lawn (and
area which looked like a rather ugly 'hump'), I decided to excavate.
Having found concrete about 10cm under the turf I eventually found a
concealed manhole cover.

On investigation I seem to have found a disused cesspit made of
concrete, with iron supports inside, measuring about 5 metres long, 3
metres wide and 3+ metres deep. It seems to be totally empty albeit
there is 30cm or so of water at the bottom. I do know that my house was
connected to mains sewage about 15 years ago, and I had assumed the cess
tank would have been filled in or removed. I can not see any outlets,
which has led me to conclude this is not a septic tank. There is one
inlet pipe which is not connected to anything as far as I can tell, I
suspect the water seeps in through this pipe from the garden above.


I agree with Mike, use it to store rainwater for the garden by directing
your gutter downpipes into it. You will need to get down into it to paint
the sides and bottom (if you can empty it) with a waterproof paint but then
you will have your own garden water supply. It can be planted over with
alpines or similar that don't need a good depth of soil.

Alternatively turn it into a swimming pool or garden pond, the depth would
be excellent for Koi but without a bottom drain I wouldn't go down either of
those routes.

Didn't one of the Garden TV shows some years ago do something with a similar
structure and turn it into a sunken garden room complete with TV etc? It was
a large Air Raid Shelter and they took off the top and made a raised one out
of glass with steps leading down.

--
Regards
Bob Hobden