Filling material pit for garage driveway

Hello community!

For us, it will start in the next few weeks and we have a question. The plot has been purchased and the development is almost finished.

In the course of the development, the municipality excavated a hole about 1 m to 1.5 m deep and 7 m x 10 m wide on our property, because old clay bricks and concrete debris from an old barn were found at this spot.

The municipality offered us the following solution: filling the "hole" with soil that arose during the development.

The problem is that in this area our garage and driveway (11m x 6m) are located, and only a smaller part covers the foundation pit for the house (with basement).

Is it worth filling this hole with normal soil (loess clay, alluvial loess) and compacting it with a roller?

Our general contractor advises us to fill the whole with crushed stone and to discuss the additional costs with the municipality. The normal soil cannot be compacted well and there is a risk of subsidence over time in the area of the driveway.

What are your experiences with this and what can you advise us as the next steps?

Thank you very much!

What would the additional costs be? I would take the advice, have it calculated for me, and talk to the municipality. If my house were to sink, I would xxxxxxxxxxxxxxxxx

I would fill with mineral mixture. Clay is difficult to compact. Gravel must have different grain sizes with a very fine portion. It should also be noted that it is filled and compacted in layers. If you fill the entire 1 - 1.5 m at once, even with a heavy roller the lower area will not be compacted and eventually the whole thing will sink. The material should also not be completely dust dry.

Good morning everyone,
thank you for your answers.

The house would not be affected, as we are building with a basement and the area around the house would have to be dug even deeper anyway. It only concerns the garage and driveway.

The gravel would consist of different grain sizes (coarse at the bottom, gradually finer towards the top) and would of course be compacted layer by layer.

The additional costs have been estimated at around €4000 to €5000; we will receive a concrete offer once the surveyor does the rough and fine staking out and can then say exactly where what stands.

I had already thought that clay is difficult to compact. But I wanted to hear your experiences and assessments.

Best regards
Sushi