I missed your post while I was typing Esshup, I have always been told epoxy coated rebar was there to combat salt damage, which occurs even if you have them in concrete, and hastens a bridges demise. The rust causes the concrete to spall and crack away, and weakens the structure. Obviously a bridge replacement being quite costly they want to avoid this. I would think you would suffer some weakening on a pond dock pier the same way, but it would take 50 years? for them to get really bad and I doubt they would cause trouble even then, being contained in the PVC. Just my thoughts, however misguided or obscure. I wouldn't expect too much trouble from that.
