Bentonite will seal it as good as any natural pond and you can reshape,
dredge or use an excavator on it without draining it. I would suggest you
get a small piece of HDPE and put some gravel on it and have the horse walk
on it before you decide. Make sure it is rounded gravel and a foot thick.

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"peter p@n" wrote in message
...
| That is a very large area for a liner and will be expensive. If it is
| seven feet deep and the soil is compacted it should be able to retain
| sufficent level as a wildlife pond, depending the rainfall in your
| area or if there is a natural spring feed.
|
| I dug the hole years ago and compacted the soil, but when I fill it (water
| from a well) the pond gets empty in a couple of days.
|
| What is your plan for filtration? Is HDPE the stiffer, thinner stuff,
also
| called Permalon?
|
| What do you mean with filtration?
| Yes, HDPE is high density polyethylene (like Permalon)
|
| Have you considered sodium bentonite? A natural lined pond is usually the
| best choice for wildlife. Why do you say you have to use a liner?
| Dave
|
| I considered sodium bentonite, I' d like it, but it implies a lot of soil
| moving and waterproofing is not 100% sure.
|
|
|
| The main factors in the selection are duration and sturdiness ( maybe my
| horse could decide to take a bath...)
| anyway I plan to protect the bank with stones and gravel.
|
| thanks to all
|
| pp
|
|