I don't know how shallow you intend to bury it, but I'd want to use a
digger for this. Even a 400mm trench 40m long would take a couple of
days to dig by hand, and that's in reasonable soil. If it's particularly
rocky then that could easily doub
Assuming access is not a problem money spent hiring someone with a
digger for a few hours would be well worth it.
royall at which net