Modeling the hydrogeological impact of a containment cut-off wall
in the Venice industrial harbour
A. G. Bernstein
Environmental Engineering Dept. - Consorzio Venezia Nuova, Venezia,
Italy
A. Paris, S. Venturini
Technital S.p.A., Verona, Italy
P. Teatini, G. Gambolati
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
ABSTRACT
A modeling study that has been carried out to quantify the hydrological
impact of a 56.8 km long cut-off wall that the Venice Water Authority is
currently building along the banks of channels of the Venice industrial
harbour. Since the soils and the groundwater in the harbour are highly
contaminated by chemical pollutants, the diaphragm is constructed to prevent
the flow of polluted groundwater from the harbour subsurface to the lagoon
area and to avoid the channel erosion and hence the transport of polluted
sediments into the lagoon. An advanced three-dimensional (3D) finite element
(FE) flow models has been implemented with a realistically detailed
lithostratigraphic sequence of the underground study area and has been
calibrated against available piezometric records. The modeling results show
that the completion of the cut-off wall is expected to abate the present
groundwater discharge into the lagoon by 85% and to produce, however, a maximum
1 m rise of the phreatic level inland over 10 years, with a serious increase
of the flooding risk in the nearby urban centre of Mestre. Consequently, the
model is used to evaluate the effect of a drainage system associated to the
barrier in order to mitigate the predicted groundwater level increase. Finally,
the model outcome suggests the possibility of a significant flow leakage
through deep abandoned wells used for industrial purposes over the 1950s-1960s
and improperly plugged in the early 1970s when groundwater pumping was
drastically reduced to counteract the land subsidence in Venice.
