SPEED CONTROL OF GROUNDWATER FLOW BY MEANS OF INJECTION-EXTRACTION WELL SYSTEMS IN A URBAN AQUIFER (MILAN, ITALY)

The high groundwater velocity can produce subterranean erosion, damaging the building excavations. The area of Milan is particularly exposed to the problem of subterranean erosion which can occur during foundations for buildings, because of the continuous piezometric level increase in last year. Therefore, this paper examines the possibility of creating areas where the flow velocity is very low (“stagnation areas”). This is achieved both by means of recharging and pumping wells, located at suitable distance. The location of the wells, their depth and flow rate can be obtained with analytical calculations or numerical models, prior knowledge of the hydrogeological parameters of the aquifer. Considering the low cost and ease of performing this intervention, it is applicable to practical cases. In order to verify the conditions of employment, it is presented a real example of using this method which are compared with the results obtained by numerical modeling.