I agree with Char. I would be more concerned about what the pipe is there for. As a registered garden here in the state of Michigan, I am constantly getting warning letters from pipeline companies to always watch where I did so that I do not hit any pipelines. I am not a huge commercial daylily garden just a backyard gardener so those warnings really don't apply to me but I do know where are natural gas pipelines are and I avoid those. I think water pipes would be down too deep to really give you any trouble but I would worry about gas lines.
