Prepare a firefighting pond for the construction site

Wow. My post about the houseboat was meant rather jokingly, but they actually managed to do it that way.

It was just a suggestion :)

Roughly calculated, 800m3 need to be filled.
A soil surveyor said it would be possible to fill with excavated soil from another property, which we would get delivered for free. He would come by in layers and do compaction tests to check if it is properly compacted.

And what if it is not properly compacted? I would assume that case if any soil from neighboring construction sites is dumped here. You need a plan and costs for this. Only proceed with further planning with these figures.
If, against expectations, it is sufficiently compacted, all the better. Just don’t plan on it.

Can you plan the house so that it does not stand on the fire pond.

We have filled a vaulted cellar and slurry pit. Not with soil, but mineral mixture because it is more compactable. We were advised against using soil. Only a small part is built over. After 3 years, it has settled slightly in places. Surprisingly little.

Build on a guided pontoon. Then you can even leave the water in the pond.

The decisive factor for the soil to be filled is its compaction ability. Cohesive soil is already ruled out because it will settle over many many years. You are only on the safe side with deep foundation (bored piles, well foundation [o.g.]). However, this would only apply to the house and possibly the garage. Paved areas ([Zufahrten, Terrasse o.g.]) I would only construct many years later, whereby further settlements cannot be excluded. A soil report with the pending soil and layer heights is initially the first step for an assessment.