[TrickyDick]

I need some advice on a job I am attempting to price. It is a little complicated so I hope I can describe it well enough.

The job is the construction of a small, very formal garden at the top of what is currently a long, moderately steep slope covered with vinca, blueberries, ledge rock and shade trees. The design calls for building a level terrace, about 50 feet long and 28 feet out from the top of this slope that will contain hedges, perennial gardens and a formal grass path and octagon edged with 6 inch bluestone sill-stock on a concrete base. This will require building up the soil at the outer edge of the terrace about three and a half feet The bluestone edge of the octagon will be only 3 feet from this edge. Beyond that the design calls for the soil to slope down the hill and meet the original slope which will create a pretty steep slope away from this terrace (I have no real idea but probably between 2:1 and 3:1). It is further complicated by a few larger shade trees that limit how far out this slope can go without burying them. There is no retaining structure involved and my physics intuition, which is usually pretty good, tells me that if installed this way this garden will slowly slump downhill.

Problem is I have no experience with this situation so my intuition is all I'm going on. I don't want to tell the client that this won't work this way without having a better idea. What do you all think? Is that enough info? Did it make any sense at all?

[dan deutekom]

Originally Posted by TrickyDick

and my physics intuition, which is usually pretty good, tells me that if installed this way this garden will slowly slump downhill.

From your description that is what my intuition tells me too. I think you should have a retaining wall or perhaps some ledge rock strategically placed to help hold this up. Hard to really say for sure without measuring and eyeing things up.

[Stonehenge]

So it sounds like you would then be building this on roughly 3' of soil you brought in to meet the new structure. If I'm understanding that correctly, during hard rains you could probably watch it begin to move down the hill. At the very least you'll need compacted, crushed stone, but my preference would be a retaining wall of some sort.

[TrickyDick]

Thanks for the help guys. I felt better going back to the designer after a little reinforcement. We decided to build a boulder/ rip-rap retaining wall below grade to hold up the terrace. Now we have to see if the client will buy it with the added cost. But at least if it gets built I will feel like it was done right.

[jshilan]

Tricky, I had a project similar to this about 20 years ago. Unfortunately I didn't listen to my "inner landscape contractor" and kept filling the yard and increasing the % slope. A couple of hundred yards later, I realized that I was right and I needed a retaining wall.

The good news is that I spoke to the client, they saw the problem too and were willing to pay for a wall. The bad news is that it was a lot easier dumping the soil down hill then it was trying to excavate with a six foot bucket. (I didn't have a backhoe attachment at the time).

Naturally I lost money on the project, but I did learn two valuable lessons:
1. Gravity is not theoretical.
2. That emergency window in the back of the Bobcat pops out real easy when you need it to.

Sounds like your doing the right thing for your client and yourself.