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A challenging follow-up project to the Julianakanaal widening project
Having previously installed no less than 500,000 m2 of bentonite mats in record time during the widening of the Juliana Canal, the outer harbor of the West Chamber of Born lock complex is the final piece for Naue. A project smaller in size by a factor of 20 than the earlier work, but more challenging in complexity.
Naue's involvement in the Juliana Canal began in the spring of 2024, says Rijk Gerritsen, technical director at Naue Netherlands. “At that time, we started intensive field trials to test the bentonite mats under the specific conditions of the canal. Those conditions are unique: heavy hydraulic stones and even concrete are applied on top of the seal for protection. All conditions that place high demands on the robustness of the sealing system. In the practical tests, the bentonite mats were exposed to extreme loads by, for example, pulling ship anchors over the stone lining and driving over them with cranes.”
Naue's Bentofix® bentonite mats came out damage-free from all field tests. The field tests gave high confidence in the robustness and durable sealing performance of the material. “For high-quality sealing, our mats are constructed with high-quality bentonite powder. In contact with water, this causes them to swell homogeneously to seal,” Gerritsen explains. “In projects where we took samples ten years after construction, our bentonite mats were found to still be at application specifications. That says something about the longevity and robustness of the system. It was therefore clear to both Rijkswaterstaat and main contractor Van den Herik Sliedrecht which type of bentonite mat had to be applied at the Westkolk of Sluis Born.”
The lock chamber was used as a temporary sludge depot during the widening of the Juliana Canal because all the sludge released from the canal could not be disposed of immediately. The silt has since been removed and the entire western outer harbor has been cleaned up. Now the necessary bottom protection is also being installed in this last section.
According to Gerritsen, the bentonite mats used by Naue are in the heaviest category, weighing almost 15 kg/m2 and with thick protective webs. An integrated sand layer protects the mats during the application of the stone layers. Although ‘only’ 30,000 m2 of bentonite mats are being installed in the West Chamber of Born lock complex, the complexity is considerably greater. “In contrast to the relatively rectilinear earlier canal route, the lock chamber has numerous recesses, mooring posts, sheet pile walls and densely scheduled work,” says Gerritsen. “The bentonite mats have to be connected to mooring posts and sheet pile walls in geometrically extremely challenging shapes. In the process, several work streams interlock continuously: replacing mooring posts, installing the seal and then installing the heavy hydraulic bricks on top of the mats.”
Naue's team handles the total package: design, delivery and installation, just as in the previous phase. “This integral approach, combined with the trust between client, contractors, subcontractors and suppliers, makes it possible to realize this kind of complex project at a high pace and with high quality,” Gerritsen emphasizes. “With all parties in one construction site, the lines are short and choices are made jointly and quickly. This approach is now even used by the Association of Hydraulic Engineers as a textbook example of modern cooperation within infrastructure projects. Looking back at what we accomplished with all the project partners in widening the Juliana Canal with only nine months of construction time would have been totally impossible otherwise. This makes everyone incredibly proud.”
Naue's team will install bentonite mats in the West Creek from late October to mid-December 2025. In February 2026, the temporary dam will be removed, after which the remaining part of the seal can be installed and the water reintroduced. This will make the Westkolk outer harbor ready for the future again.
