ᐅ Earthworks, soil investigation: how much soil needs to be excavated?

Hello,

we need help interpreting the geotechnical report. We want to build a single-family house with a slab-on-grade foundation. Our earthworks contractor would like to know how much soil needs to be replaced or compacted, but we cannot make sense of the report. I hope someone experienced can assist us. The soil conditions are shown in the attached images.
What is meant by “soil” / “bedding layer”?
What should be placed under the gravel / blinding layer, and how deep should it be?

Give the groundwork contractor the soil report; they need to be able to read it. Do you not have a site manager? They have to coordinate this!

Thank you for your reply! Unfortunately, the excavation contractor cannot make sense of the soil report, so here is my question. The construction manager was also unable to provide any information and does not coordinate the excavation work, so we are left to handle this ourselves. It would be helpful to know how much soil needs to be removed. Here is another picture showing the replacement soil and the natural ground. In my opinion, it is only from +9.27m to +9.50m (30.4 ft to 31.2 ft) of replacement soil, meaning that only about 23 cm (9 inches) of soil is supposed to be replaced. Is that correct?

Sorry, but you are even less of an expert than the earthworks contractor. You should consult the geotechnical engineer again and have them explain it in plain English or provide instructions for the earthworks contractor.

Alright, we will do it that way!

This is usually clearly stated in the foundation recommendation as well.
So, what is cut off in your screenshot. For example, mine says:

Humic and filled loose rocks, including construction debris, must be removed from the foundation area and replaced with a foundation bedding layer made of sand. Excavation must be carried out down to the top of the natural soil.
Such a foundation bedding layer must be installed and compacted in layers. Each layer must achieve 97 to 100% Proctor density. Before installing the bedding layer, the natural soil and the base of the strip footings must be compacted again.
According to the probe results, in the area of the probe, a removal of 0.5 to 1.0 m (1.6 to 3.3 feet) of filled, humic displaced material is to be expected. In some locations, a greater thickness is possible.

This means it should be replaced down to the natural sand layers I have. In my case, this was 50 to 100 cm (20 to 39 inches). Since uneven excavation is not possible, 100 cm (39 inches) was taken.

Based on your latest sketch, I would assume the same for you, since the lens of glacial clay is unlikely to be load-bearing.