Due to the construction of a new sewage treatment plant in Amsterdam, the present sewerage system was extended with a 49-km long pressurized sewage pipeline to transport the wastewater to the new treatment plant. The final piece in this gigantic project, which has become known as the “A4-project”, was a borehole drilled horizontally under the IJ. Visser & Smit Hanab carried out the drilling and the laying of the connected pipe sections.
