Earthworks for the location determination of supply lines

Hello everyone!

I want to build a house, but first the routes of some supply lines running across my property need to be clarified. I already have a rough idea of where the lines are located, but I need to know exactly in order to assess whether they need to be relocated or if they can remain where they are.

The following lines are involved:
-Gas
-Water
-Sewage
-Telephone
-Electricity

To definitively determine the location of the lines, two or three trial trenches would need to be dug. Anything else would be too expensive and too imprecise.

The trenches would need to start about 50 cm from the boundary and then be dug a maximum of 3 m into the property.

The following questions arise:
-How deep are such lines usually located?
-Who does this cost-effectively? Recommendations in the Hamburg area?
-Can a small excavator be used for this (especially the risk with the gas line)?
-Does the position of the lines have to be "officially" confirmed or surveyed, or is it enough to do it yourself and rely on that?

Before anyone asks: Of course, I have already inquired with the utility providers and received plans, but they are not accurate enough. It’s a matter of a few decimeters, as the property is quite small.

The property is located in Reinbek (20 km east of Hamburg, belongs to [Schleswig Holstein]).

Thanks for any help, and best regards,

Björn

*grins* - yes, I can sing a song about the 'accuracy' of Telekom plans, it only took a spade to cleanly cut the line of a multi-family house on a Friday afternoon - according to the plan, the line was supposed to be led about 5m further into the house... But the BBN emergency deployment was suddenly free of charge after showing the plan ;)

A mini excavator can also cause quite a bit of damage, especially with lines about 50 years 'young' where the route tape is not present at all, and such a cable hit can be expensive (although, if you have obtained the plans in advance, isn't the accident liable as well?)