Circular steel in primary dam

The construction of tidal Marnewaard is one of the three ecological linking projects within the dyke reinforcement Lauwersmeerdijk - Vierhuizergat, in which a tidal culvert will be realized right through the primary flood barrier. What makes the project completely unique is that the tidal culvert is being built in a cofferdam with purlins and struts made from used steel. A first! Thanks to close cooperation between Heijmans Funderingstechnieken and Lommers Welding Service. 

The dike passage will be formed by a tidal culvert, which in turn will be built in a temporary cofferdam structure 100 meters long by 12.6 meters wide. "In the preliminary stages, we had put forward the idea of realizing the purlin structures and outrigger frames with steel that had been used before and was in storage with us," says Roy Kerkhof of Heijmans. "However, you can't just reuse steel if you look strictly at the standards imposed. And certainly not as part of a primary barrier, for which consequence class CC3 applies and where the steel properties must be known. Together with Lommers we started a research project to see if we could upgrade the used steel and use it for the cofferdam in the primary flood defense. At Lommers they not only have expertise, but they also dare to innovate."

Extensive research

New steel comes with a certificate that describes, among other things, its technical properties. "With used steel, these data are sometimes no longer available, apart from the fact that the steel has already been through all sorts of things," says Raymond Brand, welding coordinator at Lommers Welding Service. "Based on the latest version of the NTA, since 2023 it is possible to use used steel under this heavy standard, provided the client allows it and it is demonstrated that the used steel meets the requirements and is therefore in fact equivalent to new steel. We first subjected the used steel from Heijmans to a visual inspection, from which a first selection was made. Then the steel quality and weldability were tested via non-destructive and destructive testing. The mechanical properties were verified by an external laboratory for a 2nd-line inspection. We incorporated all this information into a document similar to the original certificate, demonstrating that the donor steel meets the requirements."

Execution class 3

Of the 200 tons of steel required for the purlins and struts, over 90% was filled with used steel. The remaining 10% is new steel, as this portion was rejected during quality inspections and was therefore completed with new steel. Lommers also provided all welding on site under execution class 3, including the underlying welding documentation. Meanwhile the cofferdam has been delivered and Combinatie Waddenkwartier has started the construction of the tidal culvert. In a year the cofferdam will be dismantled again. All the steel is assembled and numbered in such a way that it is traceable for this project, but also for a circular use in a follow-up project. It is one of the first projects in which used steel is successfully upgraded for circular use on this scale and under these heavy standards. 

Innovate

This project is typical of the comprehensive service Lommers Welding Service serves. "We work a lot on projects both on site and in the workshop where an execution class according to the NEN-EN 1090 and/or the ROK is applicable. We like to think along in the preliminary process to take on projects in a sustainable way, and dare to innovate in the process, even if it may not be the easiest way," says Gerda Lommers. "Over the next few years, the infrastructure sector is facing a huge replacement and renovation task. We think integrally with our clients, so that together we arrive at a robust design with a feasible design for execution. We know how to stay within planning, project requirements and budget through 'smart' execution methods. That is truly unique for a steel engineering company. We have our company and all our employees continually developed so that we can successfully take on all V&R assignments and future work."