Backfilling due to groundwater

Sorry, I expressed myself incorrectly. So I want to fill the depression on the property with the topsoil from the excavation. It of course does not lie under the house, but in the garden in front of it.

I also made a mistake: the information on the site plan were not cm measurements regarding the groundwater level, but m measurements and mean the height above sea level, sorry.

So all the fuss was in vain.

Well, not entirely, because the filling is already necessary since the slab should lie above the street level for rainwater drainage. The property is a forest plot (pine forest with sandy soil, groundwater several meters deep) which has become very uneven due to clearing.

I would like to thank you again very much for your answers, that was very kind.

Best regards
MagNoona

Ok, so yesterday was already April Fools' Day and I totally fell for it,

so if it's not 25 centimeters but 25 meters above "normal zero," then read off a few elevation points from your expensive survey plan that the surveyor set! Then calculate the difference to the 25 m. In this way, you should know how deep your groundwater is, assuming the 25 m are correct!

Regards