How much additional cost according to the structural engineer's calculation?

I would want to see the landfill invoices at the end though. How far away is the landfill?

The earthworks contractor surely has a construction site where fill material is needed.

Oh, you sweet little naive one, really adorable.
Do you think we only charge the customer for the trip from the last customer when several are visited in one day?
The customer basically pays for the trip from the "headquarters," even if I worked in a hall an hour earlier and just walk over.
Anything else would be a nightmare because you would have to constantly charge the customer for changing trips...

Of course, you can gladly request the landfill invoice. If you do that after signing the offer, the earthworks contractor will probably say, "No, that’s my business, you accepted the price..."
If you demand it beforehand, he will probably say, "Then you can take your stuff away with your car trailer yourself..."

That’s just how business works...

Oh, you sweet little naive one, really adorable.

How do I, as the supposed quoted person, end up in this quote???

Good question... was not planned that way...

Seems to be a problem with the forum software. I also had a wrong quote in the box yesterday.

You can of course request the landfill invoice. If you do that after signing the offer, the groundworks contractor will probably say, "Nope, that's my business, you accepted the price..."

You still owe him the disposal certificate.

Why? The civil engineer offers to take away the soil for the price of xyz and to "dispose" of it. If he is not foolish enough to explicitly write that he takes the stuff to a landfill, then he can "dispose" of it however he wants.

Of course, you are free to demand that he really takes the stuff to the landfill. But then it has to be fixed in writing somewhere before you sign.

And if he likes you (which is probably not the case here judging by his behavior), he might offer to dispose of the soil inexpensively somewhere at another construction site.

But even if he is nice. It may be that he currently has no construction site nearby where he would need to fill in. You cannot expect him to dump your soil in his yard until he might need it in a few weeks.

Here in the construction area, huge piles are still lying around where those started later. People will have to have them hauled away, there is no one left who can use large amounts of clay on their site.

When construction was going on everywhere, the civil engineer transported almost 100 m³ of soil for 0 EUR/m³ from the neighbor, only costs for the truck because he was driving here daily anyway.

But you do not have a claim to that, it is important to understand.