Pilot area
The Milan metropolitan area is one of the most populous in Italy and in Europe. The local public administration have been involved in the project FOKS, in particular the Office for Reclamation Plans, which has the role to authorize the remediation intervention on soil, subsoil and groundwater, on municipal territory.
The pilot area is a wide zone of about 5 ha; it has been chosen among the critical areas in the north-east part of the city for the contamination by Chromium VI.
Aerial Photo of Milan area
Complex hydrogeological conditions
The groundwater contamination within the city boundaries, due to past and current industrial activities, consists of a complex contamination pattern, characterized by different types of contaminants spread over large areas.
To understand the local groundwater condition, to know the main characteristic of the Milan groundwater is needed. It is a multi-layer acquifer; in the north-east of the city there are some connections between the first and the second layers; this area can also be seen as a collecting point of the water upstream regions (where there is an high presence of brownfields).
Protection of all the layers is an important issue. These characteristics are critical because the second layer is usually used as drinking resource: protection of the first layer means also protection of the drinking resources.
The distinctive hydrogeologic structure and the urban context lead together to the high vulnerability of Milan groundwater. Due to the complex hydrogeological conditions and the overlapping of different plumes the identification of liable polluters will be a challenging task.
The Milan Contamination
In 2003 the Office for Reclamation Plans pointed out a Monitoring Civic System, made up by 100 wells, belonging to different bodies and offices. The aim of Monitoring Civic System is to have a direct control tool for first groundwater layer, which allows the management of the territory by the Municipality, and a direct acquisition of both physical (as groundwater level variations) and chemical data.
Heavy metals (like Chromium VI) and a spread contamination by cancerous aliphatic chlorides are the main pollutants of Milan groundwater.
The pilot area is a wide zone in the north-east of the city. It is characterized by a clear plume of Chromium VI, in the first layer, which seems to threaten the close pumping drinking water stations. In the pilot area there are already about 20 wells of monitoring civic network and five pumping stations for drinking water: only GORLA drinking pumping station is actually hit by the CrVI contamination.
Groundwater contamination by Chromium VI in Milan.
Integral Groundwater investigation
On the basis of detailed data collection and data analysis the hydrogeological model will be implemented. The project foresees a optimized investigation (Integral Groundwater Investigation), which will allow the evaluation of pollutant plumes and the identification of the contamination key sources on large areas. In the pilot area the GORLA groundwater drillings will be used to apply an Integral Pumping Test, which is the core of Integral Groundwater Investigation, to study the second level of groundwater.
The IPT will allow to obtain the pollutant concentration, but also the mass flow rates of groundwater contaminant. The mass flow rate will later be used as the base for identification and ranking of key sources of groundwater contamination; besides the backtracking technique will allow to advance an hypothesis on the sources of contamination. After the first analysis, an other little control plane will be realized to check the presumed sources. Then it will be possible to think about some hypotheses on remediation and mitigation measures.
The new approach could be useful both for public authorities, which have the task to investigate and manage soil and groundwater contamination on a large scale, and for private subjects because it would enable to restrict the source zone at sustainable costs.
