1350 tons of earth excavation for a single-family house

700 tons??? That is approx. 400m³!!! That is the size of the entire excavation pit for a small house (with a basement!!!)!!! As a mathematician, I don’t need to tell you that is about 11 x 11 meters and 3 meters deep!!! By the 20cm I of course did not mean the total amount, but a layer during compaction, layer by layer...

Hmm. Everyone calculates differently... I will probably have to consult a specialist. I was offered recycled material for refilling. Not quality checked. We are not in a water protection area. Is there a significant difference between tested and untested?

Yes, that the material that is perhaps tarred or contaminated with oil without being checked is included. Although those are hazardous wastes.

Often, unchecked materials are full of wood and other waste, so one should definitely take a look at the material.

700 tons??? That is approx. 400m³!!! The entire excavation pit for a small house (with a basement!!!) is that big!!! I don't need to tell you as a mathematician that this is approx. 11 x 11 meters and 3 meters deep!!! By the 20cm, I obviously didn't mean the total amount, but a layer during compaction, layer by layer...

You calculated correctly. 720 tons. The base area is a bit larger.

So ... I have now measured the excavation pit myself again. It was not so easy because the property has a slight slope.
On the mountain side left 4m, mountain side right 3.5m
On the valley side left 2.1m, valley side right 1.9m (height from top of gravel layer to ground level)
12.1m X 10.7m base area at gravel layer and 15.8m X 15.4m hole at ground level.
Calculation:
12.45 X 10.7 X 3.1m (average height) = 412.97m3
12.45 X (2.1 X (1xsin60) X 2.1 X 0.5 = 19.08m3
12.45 X (3.75 X (1xsin60) X 3.75 X 0.5 = 60.84m3
10.70 X (3.2 X (1xsin60) X 3.2 X 0.5 = 38.07m3
10.7 X (2.5 X (1xsin60) X 2.5 X 0.5 = 23.24m3
= 554.2m3 X 1.8 = 997.56 tons
X 13.45/ton = €13,417.19 (calculation amounts to over €18,000!!!

Does anyone know how to calculate wet soil?