Principle of sinking projects
The general principle of a foil construction rests on the artificial creation of a polder, with a controlled groundwater level (horizontal drainage). The (waterproof) foil must then be laid at such a level that the vertical balance is guaranteed (the construction cannot float upwards). 

Positioning a foil construction in water, the so-called sinking of foil constructions, is the speciality of Genap BV. The first project was carried out as long ago as in the seventies near Amelisweerd and nowadays forms a standard manner of working in road construction and hydraulic engineering. There are also good possibilities for utility construction by installing foil constructions within sheet-piled basins.

Sinking a foil is in general 40% to 50% cheaper than the alternative of pouring concrete under water and well-point draining. Well-point draining has an additional disadvantage in that the level of the ground water in the surroundings is lowered, which is sometimes not desirable. This problem is solved by sinking the foil.