Underwater work performed by specialists

With project De Entree in Amsterdam in mind, he got in touch to talk about what Qceas does. The result: Qceas was allowed to bid with Max Bögl & Partners.

In a presentation, Wijgmans showed the expertise Qceas has in underwater works, in the broadest sense of the word. "Central to the presentation was the pouring of underwater concrete, via long, floating pipes," Wijgmans said.

Qceas specializes in the supervision and execution of projects in the maritime and civil sectors, mainly focused on underwater works. The work was awarded to them, "With the scope being the preparatory work for the underwater concrete pour, inspections, preparing the sheet piles, checking for contamination, welding work on compartmentalization, welding work on the fairing in the main fairing and applying anchorage to compartmentalization screens and the actual underwater concrete pour. Altogether quite a job."

Wijgmans continues: "The Entrance is a complex project. We issued the tender with a comment, namely that there should be a possibility for us to optimize. In fact, with our knowledge and experience, we always look for the best method of executing something, sometimes deviating from the beaten path. However, our focus is always on efficiency and quality." For example, a plate had to be welded onto a sheet piling, fitted with two rods of around 25 mm. "However, the welding detail showed a cumbersome and labor-intensive procedure. We therefore offered an alternative, an anchor rod through the sheet piling, fitted with a coupling nut. That saved a lot of welding and worked significantly faster," says Wijgmans.

Subsequently, the underwater concrete had to be pumped and the underwater concrete floor applied. For the pumping work, Qceas chose Gebr. Van Antwerpen. "We worked with a floating pipeline. There were four jacket pipes under the tramline, which were fed through the sheet piling. On one side these pipes were connected to Gebr. Van Antwerpen's pumping system, after the sheet piling the pipes floated on large and small pontoons. As a backup, we had pipe sections ready to go, should there be a blockage."

Additional work also occurred, in the form of fixing 34 drainage pipes under the underwater concrete. A gravel layer was placed over these, over which the underwater concrete was poured. Qceas worked continuously during the pour with eight men per 12-hour shift. "At the end of last year the pour was carried out, a total of 6,400 m³ pumped underwater concrete. We started on Monday morning at 9 a.m. and finished on Friday at noon. Looking back, we can only say that it was a fine collaboration, with mutual trust," Wijgmans concludes.