ᐅ Is the excavation suitable for backfilling?

Hello everyone,

I need to raise my terrace by about 70cm (28 inches) to make it level with our house. This will include 50cm (20 inches) of fill material and 20cm (8 inches) of topsoil, which corresponds roughly to 90 cubic meters (118 cubic yards) and 35 cubic meters (46 cubic yards). Permits are already in place.

I would like to have the fill material delivered from another construction site. There is a soil report available, which I will summarize as follows:

Here are some recent photos:

The soil is described by the owner as clayey. Do you think I can use this material safely for the fill? The note about soil moisture in the report is a bit concerning to me.

Additionally, below my retaining wall, there is a slope that levels out at the bottom. The area has been disturbed by wild boars. I want to roughly rototill it now so that I can later maintain it with a flail mower. Are there any appropriate machines available that can handle areas with stones?

Is the soil contaminated in any way? For example, geogenic arsenic? The report only provides information about soil classifications. However, if the material is contaminated, you are not allowed to use it without proper treatment.

I’m still not entirely clear where and how you plan to use the material. On the slope? How will you stabilize it there?

We are currently using very similar material for filling purposes. It compacts well. As I said, only as a sub-base. Later, topsoil will be placed on top.

At the moment, soil is often available for free—at least here. Landfills are closed...

Our local landfills are also closed.

We filled under the terrace with a mineral mix and compacted it in layers. It was only 17 cubic meters (22.3 cubic yards). If the soil isn't load-bearing, I might consider filling the lower 40 cm (16 inches) with it.

The slope looks steep. Do you really want to deal with tilling and regular mowing?

Do you want to install this under the terrace?

If yes, keep in mind that the soil will settle even after years.

tomtom79 schrieb:

Do you want to install that under the terrace?

If so, beware that the soil will settle, even after years.

I would also advise against it. We had a large amount of excavated soil left over—50 truckloads. But in the area of the terrace and entrance, our architect only approved gravel for backfilling—tons of it. Because soil always settles.

The ground is not contaminated. Old oil tanks were removed, but according to the report, everything is safe.

The backfilling will be done above the retaining wall. The terrace itself will be properly supported with frost protection, while the rest will be grass. The area near the wall needs to be sloped.

The area below the wall will be left as is but will of course be mowed regularly. For this, it will be leveled. In the photo, it looks steeper than it actually is.