: The real question is why you are having this report prepared. The procedure is subordinate to the goal. If it is about a permit-required verification, then you can take the cheapest one. If it is about getting better cost certainty for excavation/statics (soil classes), then depending on the terrain you need several drillings to see if/when you encounter which cost-increasing material. If it is about examining soil contamination, you need several samples and the procedure is different again. So: Why are you commissioning the report?