This year's winner was Waterblock BV's Watershell, an underground water storage system. Watershell can be used for several purposes ranging from water storage, infiltration, roof gardens and insulation purposes.

Due to the dome-shaped modules, a strong construction is created. The modules function as lost sheet piling on which concreted is poured. The thickness of the concrete is important for the load-bearing capacity of the system; it is possible to use Watershell under roads and parking lots. One of the advantages of the system is that cables and pipes easily can be led through the system. Another advantage is that Watershell saves space; a horticulturist can store the water underneath the greenhouse instead of next to it.

Unlike traditional cellars, the buffer storage does not have any structural limitations in terms of its dimensions. The dome shape of the cassettes creates a structure that has a load-bearing capacity sufficient for traffic class 60 or more. In the case of an infiltration project, the soil should preferably consist of permeable sand and the sides should be formed by porous XPE sheets. Where the water storage takes the form of a buffer cellar, the floor and sidewalls should be made of watertight B-25 concrete.