When deciding to build a permanent pier for my large telescope, I decided to just put on my engineering hat and figure out a way to do it ... without a lot of outside influence. I'm using a 14 inch sewer pipe (3/4 inch thick polymer, heavy!!!), filling it with concrete and going from there. As I dig the hole in a teardrop shape, I have to cut large notches in the bottom of the pipe so that concrete can freely flow from the pipe to the ground cavity.