GRONDA highway bypass – Disposal site for the excavated soil nearby Genoa Airport (Italy)

The construction of the "Gronda" highway bypass involves the planting of about 8.4 million cubic meters of spoils, of which about 5.2 potentially containing asbestos. The area identified for the disposal of the material produced by the excavation of tunnels, is the port area overlooking the Genoa airport “Cristoforo Colombo”, and in particular the "Calma" Channel that separates and protects the airport from breakwater's overflowing. The deposit consists of a strip 180 m wide and about 3,600 m long, located in front of the airport, at depths ranging from -14.50 m asl and -10.00 m asl, obtaining a narrowing of the Channel of “Calma” from 240 m to 60 m.

The study of the effects induced by the implementation and the presence of the marine deposit requires the ability to represent the behaviour of the aquatic system in which the deposit is located. The level of detail shall be useful to identify the main changes due to the construction and presence of the work.

To achieve this purpose, an integrated system of mathematical models able to represent not only the area of the project but also a wider part of the coastal strip, which influences the local hydrodynamic and dispersive conditions, is applied.

The hydrodynamic model is the main model which is connected to the dispersive model, the model of sediment transport (which simulates the erosion / sedimentation in the short / medium term), the morphological model (simulating morphological evolution in the long period) and the quality model, with which it is possible to study both the processes related to the oxygen kinetics (primary production, debris cycle, etc.) and the variation of toxic substances, considering them conservative and also applying a degradation kinetics.

The main activities carried out were:

• Data collection for the definition of the base condition of the main environmental factors (water quality, air quality, noise condition, soil quality, etc.);
• The analysis of the interactions between environment and works.

In addition, micro-simulation of the behaviour of the contaminants was carried out, and in particular: contaminants flow through the deposit barrier and contaminants flow in sediments under the deposit

The results of the simulations were used to evaluate phenomena like: the variation of the spare time and the generation of turbidity plumes.

Special attention has been paid to the impacts associated with the transfer of asbestos materials, considering the potential release of asbestos fibers into the atmosphere and marine waters during both construction and operational phases.