I'm thinking that you're going to have to support those poles with
something other than the 2' of soil... Since you're going to have to
tie them together somehow any way, why not do some sort of pergala
arrangement. Case the pipes with the wood of your choice, tie them
together to make a nice pergala...Solves the problem of supporting
them, covers the pipes, and .......The big bonus is the plants that
grow on the pergala will disguise the heat signature from infra-red
searches... ;-)