Improved Twente Canal boosts Twente’s economy

The canal is being widened to improve the flow of larger vessels. The ports of Hengelo, Enschede and Almelo will be more accessible via the Twente Canal for ships with a load capacity of 3,000 tonnes, equal to that of 120 trucks, as a result. This will not only boost the regional economy. It also reduces the number of lorry movements in the region by around 900 per day. 

The Van Oord – Hakkers – Beens construction consortium received the contract from Rijkswaterstaat based on the best price/quality ratio. This ratio is a way to stimulate the creativity and innovative power of the market. The creativity can be found in the smart working method: first placing new planks along the front before removing the existing ones to minimise the risk of seepage. But also in the phasing that ensures the large project is realised in a relatively short time. “The project includes a pilot from Rijkswaterstaat in which we work with plastic sheet piling”, says Wilco Zeilmaker, site manager for the Van Oord – Hakkers – Beens consortium. “They are being used on a small section of the project so that Rijkswaterstaat can see how they compare with ‘normal’ sheet piling in practice. We are using geotextile on the nature-friendly banks, specially developed for this project.

“Replacing a wall of sheet piling is not a challenge in itself”, explains Zeilmaker. “The challenging part is preparing and carrying out the project in a very short time, combined with the scale of the project. Many different aspects need to be managed.” For example, the available area data does not always match the situation in reality, and vessels must also be able to continue using this important waterway during construction.

That is not easy when, at times, around 100 vessels are working on the canal at the same time. “These vessels supply and take away sheet piling from and to the central depot, dredgers, and ships delivering rocks for the nature-friendly banks. It is quite a challenge not to hinder normal shipping.” This is achieved by working in so-called trains, in sections of 750 metres long with at least a kilometre in between, so that ongoing vessels can swerve and pass.”

Deepening the canal will also remove the current layer of silt on the bottom. “This silt forms a natural seal against seepage water”, says Zeilmaker. “We remove the silt in small sections and apply a new, thin layer consisting of sand and bentonite to stabilise the seepage water flow. A design board was set up for this problem. It includes the contractors, Rijkswaterstaat, the water boards and several experts to monitor the groundwater management in the area. “We are pooling the available knowledge and experience here, so we can intervene if something happens.”

“The Water Act Project Plan stipulates that we could narrow the canal by a maximum of 50 centimetres on either side”, says Zeilmaker. “We applied for permits based on this.” However, data obtained from two test sections that we were working on showed that the current sheet piling in the canal was much more crooked than had been assumed based on the available data. “That did have an impact because the permit turned out to be inadequate.” This, in turn, raised new questions such as: how do the authorities deal with this? Will it be seen as a minor change, or will we have to go through the entire procedure again? “We consulted with the four municipalities and reached a solution that meant a new permit application was not necessary. Rijkswaterstaat amended the Water Act Project Plan, which is now available for inspection.

Zeilmaker has to deal with many different parties in his role as environment manager. “I have two interests: one towards the surrounding area with its businesses, residents and tourists and one internally because, after all, we have to be able to realise a project. I am involved with almost everything because of my function. I enjoy being able to connect all the different parties and groups.”