The first project of the new hopper dredger Seaway

      
The Seaway at Den Helder

Following the successful completion of navigation and dredging trials, Royal IHC handed over the new 31,000 m3 trailing suction hopper dredger (TSHD) Seaway to Boskalis on 20 July 2026.
Immediately after, it sailed to the coast of Den Herder in the Dutch province of North Holland.
There, it started on its maiden project, consisting of a so-called "Trench Wall Replenishment".
This is one of three types of intervention regularly applied by Rijkswaterstaat, the Dutch Agency for Water Management, as part of its coastal protection programme.
The other two types are beach and foreshore replenishments.
The current Den Helder Trench Wall Replenishment project involves placing approximately 5.5 million cubic metres of sand in a deep trench along the coast to stabilise its steep wall.
This sand originates from a mining location in the North Sea.

Morphological aspects

Trenches near Den Helder in 1926 (left) and 2021 (right)
(credit Rijkswaterstaat / Elias)

From a morphological point of view, the area around Den Helder is highly dynamic.
The situation became even more complex after the Zuiderzee was closed off by the completion of the Afsluitdijk in 1932.
Den Helder is located at the northernmost tip of the North Holland mainland.
The Wadden Island of Texel lies just opposite, and the waterway between Den Helder and Texel, known as the Marsdiep, is one of the most important links between the North Sea and the Wadden Sea.
Until 1932, the Marsdiep ran more or less in a straight line from east to west into the open sea, forming a trench known as the Westgat.
However, since the closure of the Zuiderzee caused the morphological situation to become unstable, this trench has gradually turned and shifted towards the coast in a southward direction.
The current trench runs almost parallel to the coast and is known as Breewijd in the first part and followed by Nieuwe Schulpengat.
Increased tidal currents have a strong erosive impact, creating a steep underwater cliff just off the coast of Den Helder.
Without intervention, the ongoing erosion would pose a significant risk of undermining the coast and dunes.
Therefore, regular stabilising replenishments at this location are of vital importance.

The unique configuration of the Seaway

      
The Seaway at Den Helder

The Seaway's unique configuration makes it the ideal piece of equipment for this kind of project.
Given the large volume of sand to be transported, a large hopper capacity is essential for carrying out the work in a cost-efficient and sustainable way.
However, the approach to the replenishment location near the coast is rather delicate and requires a highly manoeuvrable ship.
With two Azipods capable of turning 360°, the Seaway combines a large hopper capacity with unparalleled manoeuvrability for a ship of its size, making it the ideal dredger for this project.