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Whether the project is large or small, the challenge lies mainly in its complexity. The latter is what makes the construction of the Singelgracht-Marnix garage interesting for Boskalis. "Every day it is another puzzle with people, equipment and available space," said Kevin van den Borne, project manager at Boskalis Netherlands.
Boskalis is a specialist on land and water and enjoys world fame as a dredging company. But they do much more than this. They build structures, dikes, construct and maintain roads and ports, keep the coast safe and create new nature. In short, Boskalis is a groundbreaking multi-specialist. Boskalis' knowledge and skills also come in handy with the Singelgracht-Marnix garage. Van den Borne: "Within this project a number of disciplines come together; the complex way of earthmoving, working from the water and a difficult technique. Exactly what we are good at and why the construction of the Singelgracht garage is a good fit for us. What makes it fascinating for me as a project manager is that it is a technical challenge with schedule pressures."
Boskalis Netherlands' work was multifaceted and included the following: the dry and wet earthwork including transportation, delivering a clean construction pit ready for the application of underwater concrete, the removal of some 100,000 m3 dredged material by ship and, finally, carrying out land and water bottom remediation. Working in the heart of downtown combined with the very limited working space and the concatenation of work by various parties made it not an everyday project. "The vast majority of the work was done from the water. The dimensions of the work were also special, after all you are talking about a work 420 meters long, 25 meters wide and 11 meters deep with monumental buildings and trees on either side." For Boskalis' skilled crane operators, making the construction pit ready for dumping was a very intensive job. "It is a complex excavation because they have to work in murky water, i.e. without visibility, relying on digital excavation systems. In the cofferdam you also have to deal with underwater outrigger frames, which complicates the excavation. Largely for this reason, we also worked with a grab. At the same time, the crane operator had to keep an eye on the monumental trees. Under no circumstances were these to be damaged."
There was no room on site for temporary storage of released sludge. "What sludge we had had to be removed by smaller boats. So the challenge here was to work as efficiently as possible with as little space as possible. The 100,000 m3 dredged material was removed through the canals in close cooperation with City Barging, largely by means of emission-free ship transport. Thanks to thorough preparation and cooperation, this went well." That is also the beauty of Boskalis according to Van den Borne. "Every job is different but we have all the techniques and technicians in house to make it possible, such as a versatile equipment service and knowledge and expertise of polymers to realize the sedimentation of sludge in a very limited space. Moreover, we can make the most of our market position for reuse of soil and dredged material across the various projects."
Boskalis found the cooperation with both Mobilis and the other parties to be very good. "Cooperation with subcontractors, suppliers and other parties on the project is very important for achieving a good result. We have a good relationship with Mobilis and work together on various projects. With our specialty, we provided a nice addition. There has been joint work. This is partly due to the daily coordination on progress with all involved as well as early and intensive coordination with local parties and authorities."
