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Temporary sea wall protection at Wijk aan Zee

Location of work/project:



Wijk aan Zee - The Netherlands


For the connection to the national grid, pipes needs being drilled under the dunes in the Netherlands, through there electricity cables will be pulled for the connection of the wind farm to the national grid.

Several wind farms are being planned in the North Sea to meet the demand for sustainable energy. Among them, the Holland Kust Noord wind farm, with a capacity of 759 MW, requires connection to the national grid, a task which is the responsibility of TenneT in the Netherland.

To connect the wind farm to the grid, underwater cables, managed by TenneT, will be laid. However, a challenge arose at the landing location due to its partial below-sea-level position. Direct connection through the dunes risked flooding the hinterland.

To address this, NRG, the cable installation company, constructed a 6-meter-high sand "castle" on the beach of Wijk aan Zee. This structure allowed for drilling pipes under the dunes safely, avoiding any flood risks. The "castle" is reinforced with vertical steel sheet piles to withstand the sea's force, especially during October to March, which is the off-season for tourism, and which coincides with storm season.

Collaboration between NRG's design team and Solmax engineers, with oversight from Rijkswaterstaat (coastline management) and Deltares, led to a design incorporating GEOTUBE® marine systems and scour aprons for additional protection. Around 240 linear meters of Ø4.5 meter GEOTUBE systems were installed, with scour aprons placed underneath for scour protection.

Acknowledging the storm season's potential for damage, a contingency plan was developed to quickly replace GEOTUBE systems if needed. Rijkswaterstaat, with its focus on flood prevention since the 1953 flooding, ensured no risks were taken.

The project saw the installation of 8 GEOTUBE units by a subcontractor, using locally sourced sand for filling, which was returned to the beach post-project. Despite exposure to several storms, the systems effectively protected the steel sheet wall. Once the project concluded, the GEOTUBE systems were dismantled, and the materials incinerated.

The project was completed safely and on time, with TenneT and Rijkswaterstaat satisfied with the solution's performance.

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