Aim is to build 70,000 gravel columns in 17 months

Gravel work begunon may 4 also continues

GENOA, July 17, 2023 – A new important construction phase to consolidate the seabed is underway at the underwater construction site for the Genoa’s new breakwater. The first gravel columns that will ensure stability of the base that will support the structure began to take shape in an area named Campo Prova 1 (Test Field 1). The columns to be built are in total 70,000, and they will extend along the whole perimeter of the breakwater. As of today, about 100 have already been built. Approximately 850 of them will be built in the first month at Campo Prova 1, with the aim of completing them all in 17 months.

The work to lay the gravel on the seabed proceeds. Some 185,000 tonnes of material have already been dumped using a ship weighing 3,600 tonnes and two smaller vessels of 700 tonnes in total, which transport a daily average of 3,000 tonnes of gravel. They have already travelled a total of 90 return trips from Piombino and Genoa. 

The breakwater is being built by the PERGENOVA BREAKWATER, led by Webuild in partnership with Fincantieri Infrastructure Opere Marittime, Fincosit and Sidra. Rina is carrying out the project management consulting activities. Commissioned by the Western Ligurian Sea Port Authority, the project, which is receiving funds from the National Recovery and Resilience Plan (known in Italian as the PNRR), will create an estimated 1,000 jobs, both direct and indirect. 

The gravel columns will be built using an innovative technique named “Wet Top Feed – Blanket Method”. The technique foresees using a vibrating probe called a vibroflot, a needle-like element whose length ranges from 17 to 21 metres. The probe, connected to 40-metre-high cranes positioned on floating platforms (or pontoons), is sent down to the seabed, to a previously positioned strata of gravel, to host the columns that will reach more than 13 metres in height. Vibrating, and using combined water-air jets, the probe penetrates the seabed creating a tube-like space into which the surrounding gravel flows. As it flows, the future columns take shape, and are progressively made more compact. 

The breakwater is the largest intervention to be carried out to strengthen the Italian port system. It is a barrier that will protect the port of Genoa from large waves. A unique project in engineering terms, it will be 6,200 metres long. It will replace the existing structure, but its positioning will be further out to sea to allow access to the port by ultra large cargo ships, which as of now are limited in their manoeuvres due to the reduced space.