Economic development is an important aspect of every country or region, a proper infrastructure is vital in order to achieve this. Ports act as the gateway to global trade and are therefore a vital part of any country with access to the seas.

As such, any port construction project is important and in turn dredging works are a significant part of any port construction project. Deepening access channels, creating new land for terminals and in the end the maintenance of all shipping lanes is done with dredging. 

Many ports in Europe are investing in infrastructure to accommodate the rapidly developing renewable energy industry. A good example of this is the port of Brest in Brittany, France. In 2007, Région Bretagne became the owner of the port as part of a reform of French seaports. The port has recently had construction work carried out as part of a €220 million investment programme to maintain its competitive position and create a dedicated area for the marine-related renewable energy industry.

The creation of this new area involved major construction work on land as well as in the water. In 2017, Région Bretagne awarded two important marine contracts – one for reclamation works and the construction of a quay wall, and another for the construction of a breakwater.

Construction of the quay wall

The quay wall comprises two berths with a total length of 384 metres. The wall itself has a width of 20 metres, but behind it is a 100-metres-wide platform, creating an area of 384m x 120m, designed for heavy loads. The foundation consists of a four-metres-thick layer of gravel, representing a volume of almost 200,000m³.The gravel was dredged at a franchise of Granulats de Manche Orientale (GMO), north-east of Cherbourg. To dredge the gravel and transport it to the construction site in Brest, SDI used DEME’s 13,700m³ trailing suction hopper dredger (TSHD), LANGE WAPPER, built by Royal IHC. The distance from the GMO franchise to the port of Brest is about 265 nautical miles, which represents a sailing time of almost a whole day.

Brest port development with spray pontoon
Brest port development with spray pontoon

As a result, the LANGE WAPPER delivered its load of gravel (with a payload up to 19,000 tonnes) every two days. The arrival in the port had to be carefully planned in view of the tide. Brest has a tidal range that mostly varies between four and six metres and only at high tide is it possible for a fully loaded dredger to reach the project site. In order to accurately apply the gravel, SDI has purposely built a spray pontoon mainly consisting of modular pontoon sections, a frame, a pipe and a spray boom. At the project site, the LANGE WAPPER could connect to a floating pipeline, which was connected to the spray pontoon at the other end. In this way, almost 200,000 m³ of gravel was successfully applied up until the beginning of August 2017.

Monitoring the environmental impact

During this operation, the turbidity was a special concern due to the presence of sensitive marine species including shells, sea grass and algae, such as Zostera and Maerl. Throughout the entire process of gravel placement, the turbidity was constantly monitored. These values, determined by optical devices, were confirmed by sampling.

In the meantime, preparations were made by the other partners of the joint venture to start the construction of the quay wall. This consisted of two rows of sheet pile wall of the combi-wall type, ie a combination of tubular piles and sheet piles. The quay wall and the adjacent platform were completed in 2019.

Brest port development by Lange Wapper

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