The key factors are the thickness and the type of the soil.
What should be done is the study of the stratigraphic sections of the receiving ground (profile and thickness of the different soil layers of the natural terrain, rock profile and average maximum groundwater level, soil types: texture, structure, density, color, presence traces of oxidation-reduction, associated level of permeability, presence of organic matter, etc.).
The report should describe the classification system used to describe soils.
