The paper describes theoretical aspects concerning the influence of physical and mechanical properties of the soil in the process of epuration and self-epuration. Soil depollution is carried out by means of long-term procedures (in the case of auto-epuration) or by way of costly procedures or methods which are, technically speaking, difficult to apply (in the case of epuration), so in order to prevent the physical pollution of the soil, we need to study the properties (physical and mechanical ones) and their influence on the soil considered as filtering material.