Immersed tube tunnels are typically constructed by excavating a trench before placing large, prefabricated tunnel segments into position and backfilling the trench. Based in Trelleborg, Sweden, Trelleborg Marine specialises in total sealing systems for immersed tube, bored and cut and cover tunnels. “Immersed tunnels are among the most technically ambitious and strategically valuable assets in the built environment,” the company says. Trelleborg Marine and Infrastructure design engineering manager Jurriaan van den Berg, who is based in the Netherlands, believes the industry needs to move beyond a traditional handover mentality and embed whole-life maintenance into the design process from the outset. However, long before tunnel elements are installed, extensive testing forms an important part of the design process.