Excavation up to the sewage pipes

I suggest you talk to him about it.

and any possible documentation I would do photographically...

I would grab an expert, have them conduct an inspection, and also have them handle the documentation. It doesn’t cost that much and may later be crucial.

I also find the question of the specific agreement important. Basically, everyone has to stick to the agreements. A "use" of the property by one meter is five times what was agreed here. Now it would be important whether it really bothers you. The costs for the expert could be shared if you talked about it. After all, it is also in their interest to document that no damage could occur (there might be something later on).

In addition, one should always keep in mind that these people will be your future neighbors for a relatively long time. You have to put aside sensitivity if it doesn’t otherwise bother you and no damage will occur.

It’s like in life, only those who speak up can be helped. ;-)

Good morning,

it is interesting to read how recommendations are cheerfully given here without the OP even remotely explaining the situation on the mother’s property. I would therefore find it helpful if the OP would finally express himself concretely; without prematurely assigning him the role of the "poor" and "affected" user ;)

By the way, civil engineers are not delicate technicians who operate in the μ-range; they calculate in m³ and meters. It may also be that the soil expert prescribed a rather flat slope angle due to the encountered soil conditions ... and ... and ... and.

Of course, it would have been advisable if he (the new neighbor) had spoken up about why more excavated soil was parked on the mother’s property than agreed. Equally obvious would be if the OP approached the new builder and brought up/clarified the pending questions. Acting from supposed cover is a shot that often backfires.

A new - and usually still highly sensitive during the construction phase - neighborhood does not handle it well when cameras and/or experts become part of the house-building/neighborhood adventure unilaterally. Talking people, on the other hand – especially if they aim for a long-term good neighborhood – generally find a mutually acceptable solution ;)

Best regards from the Rhineland

And so it is as always: answers are given based on the described circumstances. If these are so incomplete that an answer is not possible, then there is no answer. If they are so "enlightening" that a recommendation for a course of action is possible, it can be assumed that no further elements exist that contradict such a recommendation.

Regarding the unloading of the excavation, there are clear agreements (according to the information / 20cm are already quite specific). These agreements were not kept, which should also be clear to the "disturbing" owner. Whether it was an excavator operator or a vascular surgeon is really irrelevant. I would have assumed that—in the case of a somewhat larger space requirement—the disturbing neighbor would ask their new neighbors for acceptance or at least get back to them afterwards. Neighborhood goes both ways, and the "newcomer" is not necessarily obliged to simply submit and swallow faits accomplis.

In the end, we agree. Neighborhood life is basically based on tolerance and consideration. Talking is always great, unless you are dealing with a real idiot (*sorry*). I also believe that a nice and neighborly approach can have a preventive effect here. ;-)