Given the problems of building a large scale layout, outside, in the limited space available, you often run into the problem of backyard “stuff” winding up smack dab in the middle of your railroad. I had this very problem with a PVC drain pipe and in this 17 page PDF document (14 pictures) show how I "hid" the pipe in plain sight.
1stclass.mylargescale.com/tj-lee/Trains%20-%20Building%20Scenery%20-%20Hiding%20PVC%20Rev%2001-01-08.pdf