I also think it is better to know in advance maybe what, where is to be built/may be built (in the garden). For example, I think above a soakaway tunnel it may/is better if no garden shed stands(?). Therefore a) one should know what is possibly feasible by an excavation contractor (of course for a fee) and b) one has a rough idea of the garden and so on. For example, where it is best to park the bicycles, garden shed, greenhouse, chicken coop, beds, sandbox (just an idea). A 3m distance to the neighbor should also be well used since the property is not really big. What will actually be fulfilled afterwards is another matter. Of course, when one lives there for a few weeks or months one knows more, sun path, wind, shade, neighbors, etc. then a lot can change, needs as well. I will list what an excavation contractor can do. I ask you for corrections and additions. I will discuss this with the site manager or the head of the company. 1. Infiltration for rainwater 2. Drainage 3. Connection of wastewater 4. Preparation for the driveway, terrace and carport (excavation and graveling)