Protecting Naples underground from water ingress

The Challenge

Building the extension to the Naples Metropolitana underground network involved driving several kilometres of track tunnel beneath heavily urbanised areas of the city and the construction of several new stations.

To add another level of complexity to the project, an unusually high water table and the city’s proximity to the coast meant tunnels and stations were subject to high water pressure during construction – and long after their completion. What’s more, the inaccessibility of any waterstop for repair or replacement meant engineers had to be 100% sure of its performance against both water ingress and vibration damage.

Our Solution

Hydrotite CJ, a composite strip of hydrophilic and non-hydrophilic rubber, provided the answer. Its unique profile creates a 100% effective double seal, first by conforming to the contours of the joint after installation. Then by expanding on contact with moisture to provide a watertight barrier against pressures of up to 0.5MPa, even after significant movement. Over 5 kilometres of Hydrotite were used to waterproof and seal construction joints and platform tunnel sections in the new stations, many of which were beneath the water table.

Results and Benefits

The new sections of the transport system are now safe, dry and protected from water ingress for their one hundred plus years of anticipated use as specified by the project commissioners. And the Neapolitan authorities haven’t just approved the stations for use by passengers and staff – they have also they made them home to an extensive public arts project.