Experience and tools from Italy for the characterization of complex contaminations in urban areas- PLUMES Project

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1 MAGPlan Conference Stuttgart 2-3 July 2015 Experience and tools from Italy for the characterization of complex contaminations in urban areas- PLUMES Project DICA-Dep. of Civil and Environmental Ing.

2 Milano FUA hydrogeology The city of Milan and its Functionl Urban Area (FUA) are located in the Po plain where alluvial and marine sediments have a thickness greater then 400 meters. 3 main Aquifers (A, B, C) are used for groundwater withdrawal and in Milan wells seldom reach a depth greater then 200 m

3 Milano FUA: hydrogeology Groundwater has a low gradient varying from 0.2% to 0.6% and for the 3 aquifers the main flow direction is from North to South toward the Po river. In reason of the high hydraulic conductivity and the high groundwater withdrawal rate Milano represents a drainage area PUBLIC WITHDRAWAL m 3 /y l/s

4 Milano FUA: contaminated sites Since 50 ies urban area and industrial activities grew in the northern part of the Milano FUA. Groundwater was contaminated for decades an still today many different plumes flow into the city and they hit public drinking wells Often groundwater need to be treated through active carbons before to be distributed in public pipelines Chemical plants Automotive Refineries Chromium plating Tires production Laundries Still production

5 PLUMES Project: objectives Lombardy Region funded the PLUMES project managed by ARPA The main aims are: To improve the knowledge of the hydrogeological structure in Milano area To implement a 3D groundwater flow model for the 3 main aquifers To collect and organize concentration data of last 10 years coming from different monitoring networks To delimit the main plumes of PCE, TCE, CLF and CrVI and to distinguish them from a background multiple-point diffused contamination To implement 3D transport models to verify which of the main potential sources could be responsible of the observed plumes To evaluate alternative strategies strategy to face the plumes spreading toward the city of Milano To evaluate alternative strategies to manage the diffuse contamination in next years To prioritize the actions to investigate and remediate the plumes To forecast through models the effects of the actions CONCLUDED RUNNING NEXT STEP

6 PLUMES Project: flow modeling The conceptual model implementation and the flow modeling phase have been concluded Milano FUA

7 PLUMES Project: monitoring network The official monitoring network managed by the Environmental Protection Regional Agency (ARPA), is regularly sampled and subdivided by aquifers But it consists of a few wells unable to give a complete overview of the spatial distribution of contaminants in an area of over 600 Km 2 WE NEED TO REDUCE THE SPATIAL UNCERTAINTY

8 PLUMES Project: monitoring network Nevertheless in the study area is present a high number of private and public wells/piezometers, where analysis are performed for different purposes at different time steps Furthermore is seldom known which is/are the aquifer screened. Consequently it was impossible to correctly attribute concentration to aquifers Merging different public database and checking stratigraphic-logs it was possible to select a number of wells representative of the groundwater quality for the 3 main aquifers The figure show the improved monitoring network constituted by points

9 PLUMES Project: plumes vs. diffuse contamination The complete data set consists of about analysis for each parameter Representing them in a map it arise that: most of the monitoring points have low-medium concentrations (<20 µg/l) probably not linked to a specific source (i.e. diffused contamination) few points show high or very high concentrations linked to a source (i.e. hot spots) Multi-point sources are so small (area&mass) that there is no chance to find and remediate them Therefore Lombardy Region, in reason to prepare a management plan, needs to define a threshold to distinguish areas concerned by a diffused contamination from areas hit by plumes

10 PLUMES Project: statistical analysis Such a huge amount of concentration data are statistically analyzed through cluster analysis and multivariate analysis Numero di casi in ciascun cluster Cluster , , , , , , , , , , , , , , ,000 Valido 45602,000 Mancante/i 26,000 Diffiused contamination Hot spots

11 PLUME Project: statistical analysis Representing in a GIS the known sources and the point of each clusters its possible to check their relationships

12 PLUMES Project: plumes vs. diffuse contamination The definition of the concentrations threshold values for Milano FUA diffused contamination follow this steps: Statistical analysis is used as a first screen to associate monitoring wells with a specific source Transport modeling for plume dimension assessment Exclusion of the points involved by the plume from the list of the points that should be used for diffuse contamination interpolation Definition of the diffuse contamination threshold

13 CONLUSIONS After 20 years of investigations and remediation actions in Lombardy Public Authorities arise the awareness that probably any remediation technology won t be able to reach concentrations so low as our Italian law limits require (0,1-2 µg/l). For this reason for the first time in Milano we are dealing with the problem of a diffused multi-point contamination in Functional Urban Areas. The main challenge is not the definition of the concentration threshold, but the management of this low CHC and CrVI concentrations in next years Any transboundary experience in facing diffused multi-point contamination will be an added value to face next PLUMES objectives: To evaluate alternative strategies to face the plumes spreading toward the city of Milano To evaluate alternative strategies to manage the diffuse contamination in next years To prioritize the actions to investigate and remediate the plumes To forecast through models the effects of the actions NEXT STEP

14 CONLUSIONS D.I.C.A. Dipartimento di Ingegneria Civile Ambientale