This will be a small dock. Maybe 12’x8’ platform. I was thinking 4 to 6 piers.
Sean,
Welcome to Pond Boss!
8" concrete pilings are plenty strong for an 8x12 deck. Even 4 of them is more than strong enough. Sounds like your driving method would work too. If the auger fits real close, I don't see why you couldn't drive the pipe pretty deep. Maybe you should wait for hot weather, because even with a wood block, the PVC will probably shatter if cold. I don't think more than 2'depth would be necessary for a deck that size. As mentioned, your problem is going to be ice, so you may need to drive a few rebars down inside the pipe before pouring. You can cheaply strengthen your concrete by adding a little pure Portland cement to the mix. 1 sack would be plenty enough to strengthen 4 piers.
I just had a thought that a small aerator at each pier would keep them ice free for a few feet around.
