Published: July 17th, 2017

In April this year we started work on what is an extremely welcome project: reinforcement of the Wadden Sea Dike on the island of Texel. Combinatie Tessel has been commissioned by the Hollands Noorderkwartier Regional Water Authority to reinforce approximately 14 kilometres of dike and to replace three large pumping stations.

The dike no longer meets statutory safety requirements. At various points the dike is too low, lacks sufficient stability and requires stronger revetments. The pumping stations have also been rejected in terms of their water safety; consequently, they need to be replaced.

In most locations improvements to the dikes are to be made by replacing the dike revetments, creating gentler slopes or slightly increasing the elevation. However, sheet piling is to be installed at a number of sites where there is too little space. Perhaps the most far-reaching work has to be done at the port of Oudeschild, where Sterk has achieved major sheet-piling construction work.

In view of the location (likelihood of damage, disturbance and tourism), nuisance levels had to be low in terms of the work to be done. For that reason, there was vibration-free installation of all sheet piling. Our approach included using our Woltman piling equipment to guide installation of the sheet piling with a leader. To that end a pile press pushes the sheet piling into the ground in batches of four (referred to as ‘quads’). You can get a good idea of this in the first video on the right (starting at 1:20):

Silent Piler
We have also managed to install sheet piling vibration-free by using our Silent Piler. This compact machine, which basically travels across the sheet piling, was implemented in places inaccessible to our other equipment. The first sheet piling to be put in place was achieved using a ‘start-up frame’. This was furnished with the necessary ballast to compensate for the compressive force on the sheet-pile planking. You can see how this works in the second video on the right..

De Schans Pumping Station
We have also been installing sheet piling at various pumping stations, including the De Schans Pumping Station. In part, this pumping station needed to be replaced because we found that the dike construction lacked sufficient strength. Moreover, this pumping station had reached the end of its operational life.

To produce the pumping station, Sterk installed the sheet piling in front of the construction pit to serve as a temporary earth and water-retaining structure. This prevented the sea from entering the site during construction. A splendid video was also made of these activities, which you can see in the third video alongside.

A significant part of the work has been completed or else is in progress. The entire project is scheduled for completion at the end of 2019.

Project details

  • Client: Combinatie Tessel
  • Location: Texel
  • Contract value: € 1.000.000 +
  • Start date: 15-04-2017
  • End date: 16-10-2017

Techniques used

(Pre-)drilling, Anchoring constructions, Construction work, Fluidisation, High-frequency vibration/extraction, Static driving, Strutting

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