Where a 'small' project Dijkversterking Stad Tiel can be big 

Over a length of 2.6 kilometers, the dike along the city of Tiel is being reinforced. In terms of length, it is one of the smaller dike reinforcement projects, but also one of the most complex. Various interests, Unesco World Heritage, monumental buildings, the construction of an apartment complex, local residents whose daily lives continue as usual plus the Appelpop festival that took place between operations, all this required intensive cooperation. The beauty of this is that it provided opportunities for so-called co-incorporation. How exactly that works, director Gerbert Ploegmakers and technical manager Robin van Dijk of FPH Ploegmakers explain. 

First, briefly about the dike reinforcement: along the city of Tiel, the dike between the Amsterdam-Rhine Canal and the Inundation Canal will be made stronger and higher. The dyke reinforcement will improve water safety for the city and the hinterland, but will also change the face of Tiel. Among other things, there will be a new quay wall and an exterior sheet pile wall. Work started at the end of 2022; the project is expected to be completed after the summer of 2024, within the set milestones. 

Different interests

"The collaboration within this project is quite unique," says Gerbert. "Apart from the technical aspects, it is the different partnerships and interests that make it challenging. The client is Waterschap Rivierenland, but in addition we work intensively with the municipality of Tiel. When working in the harbor area, the interests of the project developer of the new apartment complex to be built came into play, as did the Department of Public Works and the water sports association. And because you are working in the middle of town, you have to take into account local residents, business owners and events. All in all, a lot is happening in a small area involving a lot of different interests."

Early alignment

Waterboard Rivierenland, municipality of Tiel and FPH Ploegmakers are pulling together on the dike reinforcement work in Tiel. By tackling the project together and with adjacent residents and parties part by part, a lot of work can be done. Gerbert: "The dike is owned by the water board, the roads and bicycle and walking paths that run over it are managed and maintained by the municipality. By coordinating the work at an early stage, we were able to include linkage opportunities in our work. Co-coupling opportunities are small individual projects of the municipality, for example, that have nothing to do with the dike reinforcement, but for which it is useful if we immediately include them in our work. For example, we relocated the bicycle path near Grand Café Bellevue and constructed a completely separate bicycle and walking path on Echtelsedijk." There were also co-option opportunities in the harbor area. Here there was a vacant lot outside the dike that could not be built on.   

By placing the dike around the site, it is now inside the dike, allowing the property developer to build an apartment complex here. Robin: "The urban development in the port area was already part of the contract and therefore already included as a co-option opportunity for our contract by the water board, municipality of Tiel and the project developer. We made a particular effort to carry out the work in such a way that risks in and after the implementation phase were controlled. We have adjusted the sequence of work in such a way that the foundation construction of the apartment complex cannot harm the dike safety. Together with all parties involved, we chose to install the sheet pile walls first, then the foundation piles of the complex and finally the anchoring of the sheet pile wall. Coordination played a major role in this."

Authentic stones for city wall

The story of the apartment complex is just one of many examples of how continuous interests, safety and appearance are weighed against each other to arrive at the best solution. According to Robin, another striking example is the design of the fortress wall. There was already a final design, but FPH Ploegmakers still saw opportunities to make it even better and more beautiful. One such point was the type of stone of the monumental fortress wall. This is a recognizable point along the river. The dike passages (coupures) provide a connection between the city and the outer dike area. In the quay is the coupure Waterpoort, the passage toward the center. "From the water board's existing design, we continued working. The focus here was on the layout and appearance. Here, too, we worked closely with the municipality, the monument committee and the city architect. In detail, we looked at what type and color of stone would fit best. We even called in a specialist in Space & Quality to come up with a design that matched the old city wall and that met safety requirements and the budget. We ended up with an authentic brick, including special joints and the laying pattern, made by the Vogelensangh brick factory in Deest, which still makes the bricks using traditional methods. It was certainly not without controversy, and it was quite a process to get everyone on board. But now that the result is visible, everyone is also very satisfied and happy."

Demountable barrier

What is further special is that the dike section in the city will soon be prepared to install a demountable barrier. In this project, FPH Ploegmakers is installing demountable barriers on both new and old concrete walls. Quite diverse and at the same time complex. With a demountable barrier the dike can be temporarily, in extremely high situations, made higher (in the case of two locations on Ravelijnmuur) or closed (in the case of the nine coupures in Tiel). This solution is mainly applied in built-up areas since there are no spatial possibilities to widen or permanently raise the dike there. Because these barriers must be built manually, it does require specific management by the Rivierenland Water Board.

Innovation

The entire project also pays attention to innovation wherever possible. For example, an innovative filtering technique, namely the coarse sand barrier (GZB), has been installed in the dike section near the Amsterdam-Rhine Canal to prevent piping. The coarse sand barrier stops the formation of the erosion channel at the barrier. Groundwater can pass through, but the fine sand is stopped. Robin: "At Gameren we applied this for the first time eighteen months ago as a pilot commissioned by Waterschap Rivierenland. At Tiel we actually applied it as a measure against piping. This makes it the second location in the Netherlands. This shows guts from the water board to apply a measure that they themselves helped develop and was actually still in the pilot phase during the tendering phase, in Tiel already."

Guts to tackle

FPH Ploegmakers is an SME in terms of size. That presents challenges because they have a lot of work on their hands at times. But precisely because they work with a compact team, they can change gear quickly. Gerbert: "We are pragmatic and can change gear quickly. Our strength is above all daring to take action. The intensive cooperation with the various parties is also the beauty of this project. Every day is different. When we look at where we are now and how positive people are about how beautiful it will be, we are enormously proud of that. Because we joined together with the water board, the municipality and other stakeholders very early on in the process, we were able to keep the work on track. It has even ensured that the appearance of Tiel has become more beautiful and safer."