In the area I am at, ground water is not hard to find, meaning I will likely (even assuming I don't hit a spring) have to run at least one trash pump while I am digging. So its unlikely I will be able to compact the bottom, but no one has done it on any of the ponds surrounding me because the water table is so shallow.

Some areas around me do have hard pan at certain depths (which technically can be compacted to use as a liner), but two of the neighbors ponds were dug to almost 30' and they never hit any so I think its safe to not expect to hit any on my property either but I won't know until I start digging.

When I started clearing we discovered that the neighbors pond was actually running off onto my property, that pond is spring fed and runs constantly. We diverted the runoff last year, but did it in a way that we can easily switch it back to mine, but I intend to bury an 8" pipe from that run-off into my pond. I really feel like between that and the naturally shallow water table that I shouldn't need to.

Is that an inaccurate thought?