A really effective article from Franco Giliberto, “A conference about MoSE attracts Venice sea-goers more than the beach” talks about the zinc released in the environment by the mobile barriers anodic protection system. Twelve tons per year of this metal is a very large quantity of polluting matter, if you consider, as the IRSA (Water Research Institute of CNR, Research National Committee) expert says, that this quantity would represent by itself the 50% of the maximum allowed load for the whole Venice Lagoon drainage basin, as stated by the new City Plan.
You can easily understand why much concern has been expressed about the environmental compatibility of the continuing release of such a quantity of zinc in the water environment. Especially when you consider that the expected life of MoSE, which would develop underwater for a total length of 1572 meters, is of 50 to 100 years (the promoters themselves are unsure).
Zinc released by the anodic protection panes is a polluting substance persistent in water and in sediments and capable of accumulation along the food chain, so much that EU has proposed to ban its use in slaughterhouse devices.
Especially considering the vast areas of mollusk cultivation inside the Venice Lagoon, the figure about the zinc release should lead to think about the possible damage made to one of the most relevant items in lagoon economy, the cultivation of mussels, and the increase in the long run of the already significant difficulties in controlling the mussels quality for table consumption.
The project requires a total of 79 mobile barriers: 21 by Preporti, 20 by S.Nicolò and Malamocco, 18 by Chioggia. The average surface of each barrier is about 1000 square meters. The total external surface can be estimated around 75,000 square meters of iron, upon which toxic substances should be applied in order to try and limit the growth of molluscsand the associate biocenosis.
In the SIA the fouling growth is estimated at about 30 kg/year for square meter of mobile barrier surface, with a total encrusting production whose quantity and weight is easily calculated. It should be noted that, even if the Environmental Impact Evaluation Decree was canceled, the Environmental Impact Evaluation Committee technical report was not. That report still exists and represents an articulate and documented view, which deals with every critical aspect of the work and of its building. Now that the Plan Office is about to be started, perhaps it would be helpful to begin taking into consideration that report, given that its clearly stated assessments were never opposed with precise, well-grounded and unequivocal counterarguments.