so i went to look at a job today, and the area to be irrigated involves two zones atop a retaining wall.... first there is a ~ 8' wall, with an 8' foot wide bed atop it, and then a second bit of wall that is prob 4' tall, with the rest of the area to be irrigated. the wall runs the length of the property... its built out of 6x6 treated lumber... and was installed by the builder... so i really have no idea what it was backfilled with behind it, and i have seen plenty of builders dump concrete, bricks and who knows what the hell else to take up space so they dont have to use alot of dirt.... anyway, i could attempt to verticle bore, with water and pvc... ive got to get at least some 1" class pipe up there and my control wires... just dig a hole under the footing of the wall and hope for the best... and im sure boring right next to the wall would be easiest... but i also think thats going to be where im most likely going to run into debris... or drainage and other aggregate... im considering to run it on the outside of the wall... and maybe build a false post to conceal the pipe in..... the retaining wall was built with 6x6 posts that keep the horizonal pieces inplace. so discreatly adding a post, or doubling up a post on the end really wouldnt look that bad... plus i could cut a hole thru the 2nd or 3rd board from the top and go sub-surface again... i think if done right, i wouldnt have any issues with this, the false post could even allow me room to insulate the pipe and run control wires... now if this idea is an option, what kind of pipe should i use, is sch 40 pipe ok? and secure it with pipe clamps to the wall... i dunno, boring like this is hit or miss... and can put you behind quick... its really a simple system minus the retaining wall... thoughts suggestions please??