Earthworks: what calculation tolerance is usual?

hello,

what calculation tolerance in the offer is usual (jurisprudence?) for earthworks regarding uncertainties in the encountered soil?
When does a (non-)binding? offer become invalid?
at 20%? 40% miscalculation?

Probably one cannot insist on adherence in lump sum offers if serious uncertainties arise,
e.g. unexploded ordnance remnants or similar.

The risk of the soil lies with the client?!

Does anyone have experience with this?

First, a soil survey should provide information about the basic condition of the soil. That is already a good basis for further planning.

The earthworks contractor will ALWAYS assume freedom from unexploded ordnance and pipelines. Information about pipelines on the property can be obtained from the city/municipality/energy provider.

Unexploded ordnance is usually not known beforehand. Of course, this then disrupts the offer. The earthworks contractor is not responsible for that and is of course entitled to charge you for the costs involved upon further contract after notification. How high these costs are depends on many variables.

Short and concise: Yes, the risk lies with the owner.

That means the civil engineer cannot "just make up any circumstances" for which he unfortunately, unfortunately can/may charge more money on the spot?

Just a question, how does it actually work with unexploded ordnance finds? Here in the Ruhr area, they seem to find something like that constantly. Does the builder really pay for the disposal? I almost didn’t expect that.

Well, as a layperson, you are somewhat at the mercy of certain statements like: "We have to exchange more because the non-load-bearing soil unfortunately lies unevenly on the construction site." In that respect, you can't really verify it yourself. After all, you do receive delivery notes for the new soil and disposal receipts for the soil that was removed. Only whether that was really necessary, you won't find out without commissioning another expert report. But the time that takes usually costs more.