MO.SE project

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Map of the Venice lagoon
Aerial photo of the construction site of the MO.SE barrage at Porto di Lido, taken in 2009

The MO.SE project (= mo dulo s perimentale e lettromeccanico) is almost finished flood barrier of mobile flood gates . It is installed at the three openings (Italian: bocche ) of the Venice lagoon and is intended to protect the historic center of Venice from floods (Italian: Acqua Alta ) from autumn 2020 . The barrage is considered the largest infrastructure measure in Italy since 1945. Similar barriers are in operation in London ( Thames Barrier ) and Rotterdam ( Maeslant Barrier ) .

history

The Doge's Palace in November 1966

On November 4, 1966, the water in Venice was 194 cm above sea level. A powerful Scirocco drove seawater into the lagoon.

In 1984 the first feasibility studies were commissioned which, in addition to minimizing flood damage, also had to take into account the overall hydrogeological situation of the lagoon . For this purpose, on behalf of the Venetian water authority near Padua, a basin was built in which all the islands, all the sandbanks, the tidal conditions and fairways of the lagoon were recreated in great detail. With the participation of hydraulic engineers from the University of Padua , the effects of MO.SE on the precision mechanics of the water cycle were researched.

On March 14, 2003, Prime Minister Silvio Berlusconi started construction work with a symbolic groundbreaking ceremony . But Berlusconi's political solo effort and economic participation in the project led to numerous discussions and a national dispute.

One of the most determined opponents of MO.SE was the philosophy professor Massimo Cacciari , who was the mayor of Venice until 2010 . Even after the construction work began, he did not give up his resistance and prohibited the cost-reducing use of parts of the arsenal to manufacture components for the barrage . He was in confrontation with Giovanna Piva, who until October 31, 2010 was director of the Magistrato alle Acque .

Due to construction stops and cuts, the completion has been postponed by several years; originally, commissioning was expected in 2014. After the final tests, the structure should be ready for use by the end of 2021. On July 10, 2020, all 78 flood gates were officially opened at the same time for the first time in the presence of Prime Minister Giuseppe Conte and several ministers.

financing

As of 2013, construction costs amounted to at least 5.4 billion euros, but experts feared that they would have reached around 6 billion euros by 2014. The expected annual maintenance costs from completion are around 20 million. The project is mainly financed by funds from the Italian national budget, a 1.5 billion euro loan from the European Investment Bank , funds from Venice and UNESCO, and several foundations .

The construction is carried out by the Consorzio Venezia Nuova consortium, an association of the 30 largest construction companies in Italy. The company is based in Palazzo Morosini in the historic center of Venice. This group of companies also includes the financial holding Fininvest S.pA , which mostly belongs to members of the Berlusconi family.

Corruption scandal

On June 4, 2014, the Mayor of Venice Giorgio Orsoni and 34 other politicians and building contractors were arrested for money laundering, embezzlement and extortion in office in connection with MO.SE. An application was also made for Giancarlo Galan , the former regional president of the Veneto region , who enjoyed immunity as a senator . After Parliament lifted his immunity in October 2014, he was also arrested. A total of around one billion euros were embezzled.

Reason for construction

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The rise in sea level since 1850 and the sagging of the old town mean that the historic center (Centro Storico), which has been a UNESCO World Heritage Site since 1987 , is increasingly flooded.

The extraction of large amounts of groundwater and methane by industry on the mainland is responsible for the sinking of the old town . But also the widening of the fairways in the lagoon, the widening of the bocche , i.e. the connections to the Adriatic, and the predatory fishing are responsible. With their catch baskets, the fishermen destroy the vegetation cover on the sea floor and the water masses that are now flowing in more quickly can more easily remove the sediments and wash them out of the lagoon.

Functionality and technology

How the gates work

In the event of storm surges with a high water mark over 110 cm, the three lagoon approaches, the Bocca di Lido, the Bocca di Malamocco and the Bocca di Chioggia, are to be closed with floating barriers. The barrage consists of 78 movable elements, 18 at Chioggia , 19 at Malamocco and 41 at Bocca di Lido . There, however, they are distributed on two lines between the respective bank and an artificially created island in the middle of the lagoon opening. 20 flood gates were installed in the Lido-Treporti opening and 21 in the Lido-San Nicolo opening. The basic technique is not a new invention. The gates of large ship docks have been moved according to this principle for a long time. The flaps are large steel boxes that are filled to the brim with water when they are in their shafts on the seabed. If they are to be closed, the water is pressed out with compressed air and the gates are erected.

This is how MO.SE works, only with the difference that everything is much bigger in terms of dimensions and the doors have an "intelligent" interior built into them. Because with the size of the individual goals (5 meters thick, 20 meters wide, 30 meters long with a weight of 250 t) and the resulting forces, the up and down of the swimming boxes must be precise. These are located next to each other in their anchoring with a distance of only 10 cm. In order to prevent individual elements from being touched or jammed, air is first pressed into the tip behind a bulkhead protruding from above , so that an air bubble is formed there. In this way, each individual door can be raised in a controlled manner at the front. The flaps are not blown at the same time, but one after the other, starting from the bank, in order to let them rise out of the water one after the other.

It takes 30 minutes from the first blow to the correct positioning of all flood gates. The optimal position of the gates is reached at an incline of 45 degrees and in extreme cases can create a water difference of 2 m between the lagoon and the Adriatic . According to the engineers' forecasts, the barrage can usually submerge again after 4–5 hours when the tide recedes. So that everything works smoothly, the swimming flaps must be guided and stored securely. This task is performed by oversized frames. These are caissons made of reinforced concrete , 14 m high with a footprint of 50 × 60 m per unit. Attached to it are 3 locking flaps each on 3.20 m high and 24 t heavy hinges . In the rest position, the flaps are completely immersed in the caissons. The Malamocco inlet will be equipped with a sluice (370 m long for ships up to 280 m long and a draft of up to 12 meters) in order to guarantee the shipping traffic in the lagoon even during the flood phases. Smaller ports and locks are also provided for the other two inlets.

One of the smaller harbors on the Bocca di Lido was temporarily drained, sealed using the CSM (Cutter-Soil-Mixing) method and used as a construction pit for the construction of the caissons. After extensive testing, the CSM method turned out to be the best method for sealing the lagoon underground. This consists of unconsolidated sediments up to a depth of 28 m . These are over 95% components made from clay and fine sands with a grain size of 0.002 mm to 0.063 mm (so-called silt ). In the CSM process, the soil is liquefied with the constant addition of suitable suspensions (with MO.SE in the first step, bentonite ) and bound in a second phase by adding cement suspension . Inclination sensors built into the CSM unit simultaneously enabled the floor to be leveled with a maximum deviation of 0.2–0.3%.

For the construction of the sheet pile walls , HSP Hoesch Spundwand und Profil GmbH, a subsidiary of the German Salzgitter AG , supplied molded parts weighing 15,500 t. In view of the expected high water pressure, these were additionally reinforced with special pipes with a total weight of 7,700 t from Europipe GmbH . The CSM method was also used to seal the sheet pile walls. For the construction of the caissons, the engineers developed a special procedure: in the later lock and harbor basin on the Bocca di Lido, huge fields of stelae were created. The respective formwork is located on the man-high concrete pillars . With this system, all precast concrete parts remained accessible from below at all times. The finished caissons were lifted with hydraulic jacks and pulled for loading with the help of rollers. With what is probably the largest heavy-duty elevator in Europe, the prefabricated components weighing up to 20,000 t were then lowered into the water at the edge of the port; the MO.SE frames reached their later berths floating. The caissons were equipped with numerous air chambers that gave them sufficient buoyancy. Tug then moved the segments in place, where they with the help of GPS - navigation aids were aligned and released slowly. To do this, the air chambers were flooded. After settling, ballast in the form of crushed stone and scrap iron was filled into individual cavities to make the caissons even heavier. Inspection corridors have been set up on the front, from which the lifting mechanism and the compressed air lines can be serviced. In order to meet all environmental requirements, the installations had to disappear completely in the seabed, which - across the fairway - required 14 m deep and 50 m wide trenches. This is the only way not to hinder the given natural water cycle between the lagoon and the Adriatic. These channels are finished and consolidated. Large amounts of sand and silt were dredged for this purpose. The installation areas for the caissons have also been reinforced with 40 m long driven piles. Geotextile sheets were attached to the seabed to the left and right of the trenches. This is to prevent sediment erosion by the currents in the lagoon entrances. At Malamocco, the main entrance for large ships into the lagoon, the barrier is 14 m below sea level.

Up until now, Venice did not need any technical assistance to cope with height differences in the fairways. This will change fundamentally with the lock systems. For this purpose, a driving simulator was developed to prepare controllers for the new tasks. Since only walking pace is permitted in the area of ​​the locks, a dangerous drift occurs for the large tankers in front of Malamocco . This is due to the bora , a cold and gusty fall wind from the northeast (Croatia and Dalmatia) with top speeds of up to 250 km / h, which large ships offer a huge target.

Movie

  • Project Megabau / Gigantisch. Venice's flood barriers. (OT: Venice Flood Gates. ) Documentary, Canada, 2009, 45 min., Script and director: Karen Pinker, production: Barner-Alper Productions, Discovery Channel Canada, series: Projekt Megabau (OT: Mega Builders ), first broadcast in Germany: February 3, 2009 on Discovery HD , table of contents from fernsehserien.de.

Web links

Status of construction work on the Bocca di Lido with a new breakwater (2019)
Commons : MOSE Project  - collection of images, videos and audio files

Individual evidence

  1. ↑ Matthias Rüb: Mose gegen das Meer in Frankfurter Allgemeine Zeitung , faz.net, July 10, 2020, accessed on July 19, 2020
  2. ↑ Venice MOSE flood barriers to be handed. In: ANSA English Editions. September 12, 2019, accessed November 13, 2019 .
  3. ↑ spiegel.de: "Mose" is supposed to protect Venice (video), July 10, 2020, accessed on July 19, 2020
  4. ↑ Arrests for a dike project in Venice. Handelsblatt , July 12, 2013, accessed on February 21, 2016 .
  5. ↑ Nikos Tzermias: Mayor of Venice arrested. Neue Zürcher Zeitung , June 4, 2014, accessed on June 4, 2014 .
  6. ↑ Former Minister of Culture convicted of corruption affair in Venice. Neue Zürcher Zeitung , October 17, 2014, accessed on November 13, 2019 .
  7. ^ Karl Hoffmann: Venice and corruption. In: Deutschlandfunk. June 11, 2014, accessed November 13, 2019 .