Clarification question about soil investigation reports - removing topsoil

Hi,
I have a soil survey report which I barely understand. Could someone possibly "translate" what is written there for me?

The area is a slightly uneven fallow land with ground elevations around +0.5 to +0.7m relative height with a slight slope to the west.

Up to 0.8m: topsoil, soil class 1
From 0.8m to 1.6m: non-cohesive sands, soil class 3
Afterwards cohesive sands, soil class 4 (in case of silting class 2)

It is clear that the topsoil must be removed and disposed of or can be used for garden landscaping. Regarding the next layer (non-cohesive sand), the following applies:

[*]Bodengruppe SE, SU
[*]Verdichtarkeitsklasse V1
[*]nicht frostempfindlich (F1)
[*]Feuchtraumgewicht 18.5 kN/m3
[*]Wichte unter Auftrieb 10.5 kN/m3
[*]Kohäsion 0 kN/m2
[*]Reibungswinkel 32.5 / 35
[*]Steifemodul 20 to 50 MN/m2

After topsoil removal, a slightly different subgrade exists at about -0.15 to -0.2m. This height difference must be bridged by subbase/filling.

When performing static plate load tests, deformation moduli Ev2 of at least 60 MN/m2 should be reached at the top edge of the final gravelly-subbase.

If the foundation slab is statically designed according to the subgrade modulus method, considering a base pressure load of 125 to 150 kN/m2, a static subgrade modulus of 25 to 30 MN/m3 is assumed.

If load-bearing strip foundations are executed on the non-cohesive medium dense sand, they can be designed for a base pressure load of 200 kN/m2. This corresponds to a design value of the base resistance of 280 kN/m2.

For the backfilling of working spaces, non-cohesive, compactable fill material is recommended.

My construction specification states the following:

"The soil in the area of the building structure will be removed to a depth of about 40 cm and stored aside. Soil up to soil class 3 and a load-bearing soil with an allowable soil pressure of 250 kN/m² is assumed. The excavation will be backfilled with fill sand and compacted in layers. The base height will be filled up to about 40 cm with the excavated soil."

Since the topsoil is up to 0.8m deep, these 80cm must be removed instead of 40cm. Will there be additional work/costs for me?

Present the report to your construction company; they can give you a realistic cost estimate.

I would understand it this way: the topsoil is to be removed. Then a leveling layer is applied to achieve a flat surface despite the height difference. Then there are two options: further filling and a completely flat slab or alternatively strip foundations. I suspect it will be the strip foundations, since 80 cm of topsoil has to be removed anyway, which fits quite well.

Sounds relatively relaxed at first. Water should not be a big issue on the sandy ground.

Excavation: depending on the size of your house, you can easily expect 100m³ of topsoil, which is a huge pile.

Additional costs estimated similarly to here at around 8 thousand. More excavation is required. Unfortunately, topsoil must be removed because the quantity is too large for internal use.

Can it be found anywhere in the report whether the allowable soil pressure of 250 kN/m2 is reached? Or will that only become apparent during the earthworks?

It also says there that groundwater is only to be expected from a depth of 4.5m, and that no soil improvement measures will be necessary. Which sounds quite positive at first. In our planning, we have allocated an additional 10,000 euros for the earthworks. That could then fit.

20 mn per sqm are 2 times 10 to the power of 4 kn per sqm. So far enough, far more than the required 250.

No, it says 125 kN/m² for [Bodenplatte] and 250 kN/m² for [Streifenfundamente]. Both are completely sufficient. If the foundation is not further specified in your contract, 250 is also contractually acceptable.