What Imoore said, I have dug several of these in for heating and air contractors back in the day but every time the house was above the pond and we were digging up hill on the upper side of the pond, not anything close to or thru the dam, so leaking wasn't an issue.
They have pretty much quit even using pond geothermal in this area for some reason or other, they said they will freeze up in the colder winter months and get a very bad rate of heat exchange, even at deep depths. I don't have any clue about the systems, just repeating info.
