I'm with you John on the whole hiring of the Engineer. That sounds
very expensive. But it is a very valid point. You don't want to get
fined for dumping into the sewer or anything like that, and you
probably don't want your neighbour to take you to court for damaging
their property. I think the solution would be to do the work yourself,
but do some research (like talking to a building inspector, land
scaper, etc) in your area to see how they would solve the problem and
what the options are. That way you would keep the costs down, only use
up a little of your time, and protect yourself. As for diggind the
trech itself, what about one of those mini excavators? They're not too
wide (but I'm not sure on the width) and should be able to dig down 10
feet. Your plan sounds good to me but I'm no expert (and maybe that's
why it sounds good).