Ok guys/gals here we go. I was on an estimate today for a front walkway, with the possiblity of power raking, soil and hay for the yard as well. This home is new construction and has been lived in for about 1.5 yrs and the lot is about 1.2 acres. The front yard is a rocky mess, of rough grade leftovers, a really poor final grade and lots of shale. So with that background it gets interesting. After talking about the front yard and all the work it needs the lady and her husband ask me if I have any ideas about the back yard, I come around the house to see what I can best describe as an amphitheatre cut out from the hill they built the house into. I'm sure most of you who don't live in the flatlands know what I mean. Anyway, there is no grass on this hill to speak of and they have lost what I'm guessing is 40-50 cubic yards of soil from the hill which has washed down into the rear and side yards. They'd like a retaining wall or two, terraced if neccesary to open up the back yard for the kids and to prevent repeats of this situation. I know I'd need an engineer for this project, but what kind? Will a retaining wall engineer be able to evaluate the amount of water that comes down this hill from above? Will he be able evaluate the soil that hasn't yet washed out and advise me as to how deep my base has to be avoid a failure? Who do I need to call. I am thinking just by the size of the wall and the hold back a mountain factor that "big blocks" such as Re-con or Redi rock might be the material of choice for this one. I need some advice. We have built large engineered walls before but most of the were part of a bid, where specs were given not from the start like this one. Oh yeah I almost forgot, the owner states during really heavy rain he has seen what looks like a stream running out of the area near the wash out. My concerns here are, can I provide enough drainage behind the wall for this kind of water volume. If so will what are the chances that providing resistance to the natural flow of water force it to reroute and possibly cause issues for my base? Maybe I'm over thinking this, but I'd rather try to run through ideas here than do the wrong thing and end up in trouble.