Saving the sinking city

Press, 17 January 1986, Page 16

Saving the sinking city

An official accord, signed on behalf of the State and consortium of 31 construction and engineering companies, has launched a gigantic project for the protection of Venice from the Adriatic by means of three mobile dams.

The work may take 10 years and cost perhaps $1.5 billion. The floatable undersea defences to be installed along the three salt-water entrances to the Venetian lagoon are intended to cause minimum disruption to the harbour. The signing ceremony follows a decade of debate by experts and over five years of petty bickering involving Italy’s half dozen dominant political parties. The companies in the Nuova Venezia consortium include many public as well as private engineering and construction enterprises enjoying higjjfinternational repute. Tlje project should make Venice into a boom town.

The 1175-year history of Venice could be written in terms of an endless series of vast public work projects mounted to assure the city’s physical and economic survival. It is built on piles driven into unstable silt in the shallows of Laguna Venetia, standing in water exposed to tides and storms. And any lagoon is a constantly changing environment, a battleground between the land and the sea. The recent dramatic subsidence of the lagoon floor, and the consequent sinking of the city by nearly 15cm over 50 years, has been largely halted already by a local ordinance prohibiting the pumping of ground-water for industrial use. But the trend continues, although much more slowly, because of natural geological causes. These and other factors contribute to the increasingly freqlient surges of high water flooding the lowest points of the city, nowadays

at more than 50 times a year. A tidal storm brought St Mark’s Square under more than 1.2 metres of water on November 4, 1966, setting off a global campaign for the city’s rescue. The floatable barriers are to create an effective difference of 1.5 metres between the water levels of the Adriatic and the lagoon. The barriers will comprise three sets of bottom-hinged hollow steel canisters 23 metres tall and more than 5 metres in diameter. They will rest full of water cushioned in rubberised cradles on the sea floor across the Chioggia, Malamocco, and Lido mouths connecting the lagoon with the Adriatic. Surges of exceptionally high water can be forecast with some accuracy. Before they arrive, the canisters will be pumped full of air, causing them to float into an upright position, sealing the lagoon

from the open sea. This will disrupt the harbour traffic; but the architects of the project believe that the barriers will need to stand in place for less than 50 hours a year. About 60 canisters will be sufficient to close the Malamocco entrance, the widest of the three. Venice itself has already launched a big programame of long overdue conservation, restoration, and civil reform projects, with the city subsidising by up to 80 per cent the cost of renovating the crumbling, privately-owned palaces, many of them uninhabitable yet housing uncounted treasures. The former convents are to be turned into modern apartment buildings to be made available at reasonable rents to young Venetians in the hope of discouraging their steady migration to the j mainland. s ’ Copyright — London Observer Service.