Lateral thinking!
It seems to me you have put the cart before the horse! Use dowsing rods to find out if there is water and what depth it's at. This presupposes you know how to douse or can track down your local water divining expert. Don't laugh at the technique it really works, I have used...
I am looking for a data sheet on an obsolete modem IC, AM7911PC made I think by AMD. Someone must have a copy lying in their archives! Thank you for any replies. (Same query posted on the electrical forum by accident!