If you build a stationary dock, I would use steel pipe rather than treated lumber. A solid frame of welded pipe (We used oilfield drill stem, 2 7/8" buried 30" in concrete), with channel iron welded to the top allowed us to use brass deck screws into native cedar planks. We cut the cedar trees from our pond bottom during construction and had them cut at a nearby sawmill. I would put a dock like this one in any small northern pond.
