The article describes an urban environment and the anthropogenic factors that influence groundwater and soil conditions. Deep building foundations impact on changes in both groundwater flow and soil consistency, which may occur due to filtration phenomena. Suffusion and internal erosion were described, determining the criteria applied for assessment of soil susceptibility to these phenomena. The results of numerical modelling executed with Visual Modflow software are presented. It is stated that the creation of deep building foundations in an extensively urban area may influence the groundwater and soil conditions