Strukton Immersion Projects has successfully immersed the last of the eight concrete caissons that form the base of the storm-surge barrier near Venice.

The storm-surge barrier is being constructed at the three inlets to the lagoon, at Lido, Malamocco and Chioggia.

The storm-surge barrier is made up of a system of caissons containing movable flood gates. The immersion of the final caisson rounds off construction on the foundations for the new storm-surge barrier. The next step will be the positioning of the movable flood gates.

Strukton transported the segments – which are each 60 m wide, 46 m long and 10 m high – by water to an inlet near Chioggia on the Venetian Lagoon. The segments were subsequently immersed on site. Work on the first segment started on Saturday 7 June, with the final segment put in place on 27 August. The project demanded a high level of accuracy  - maximum allowances in any direction were no more than 10 mm.

The eight enormous caissons were built in a dry dock in 2012 and 2013. The dry dock was flooded after the caissons’ construction. After this, they lay waiting at the dry dock until they could be floated, transported to the site and immersed. Each of the 21,000-tonne concrete caissons was towed by tugboats to the lagoon inlet.

The immersion team needed to take the high local current speeds into account: twice a day, tidal movements cause the lagoon water to flow through the mouth of the inlet.

For nearly a decade, numerous parties have been collaborating on a storm-surge barrier that can close off the Venetian lagoon from the Adriatic. Netherlands headquartered Strukton, the single foreign partner on the project, is also helping Venice to combat high water at Chioggia.

The system will only be closed in cases of extremely high water, similar to the Maeslant Barrier in the Netherlands. The barrier is expected to officially be put into use in 2017.