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Sidst opdateret: 28.1.15

Recovery of Dredged Material as a Contribution to Environmental Protection

DredgDikes Research Dike
DredgDikes Research Dike

Dikes made of processed dredged material contribute to the conservation of the natural soil resources. During a four-year EU project, at which the Danish Coastal Authority contributed, the suitability of dredged material was investigated and proven. The project was lead by the Chair of Geotechnics and Coastal Engineering at the University of Rostock, Germany (Prof. Dr. Fokke Saathoff).

At many coasts along the North Sea and Baltic Sea, dikes are protecting the hinterland against flooding. For building dikes, large amounts of construction materials are needed. At the Baltic Sea coast, the standard materials are sand and clay or marl. At the North Sea coast often marsh clay is used, which is usually mined directly behind the construction in environmentally sensitive areas.

At the same time, considerable amounts of clean sediments are dredged along the Baltic Sea during the maintenance of navigation channels and harbours, in harbour construction and even due to environmental reasons. Dredged material with large fractions of fines (silt, clay) and organic matter should not be dumped in the Baltic Sea. Fertile soils are lost, which also contribute to the eutrophication of the sea. Therefore, these materials should be brought on land as it is the practice in Germany. 

There is a variety of good examples where dredged materials are processed and recovered beneficially, such as sediments from the industry and processing plant run by the Hanseatic City of Rostock.

The project DredgDikes introduced a new idea. Based on the good recovery experience, team behind the project investigated whether dredged material was suitable for dike construction and which requirements must be met when choosing the dredged material.

In 2014, the Danish consultancy Orbicon performed investigations of harbour sediments in Denmark. At six locations (harbours and channels) on Zealand, sediment samples were taken and afterwards investigated in the laboratories at the University of Rostock for comparison with samples from other locations. In addition, the study documented the legal background and the possibilities for dike construction with dredged material in Denmark. According to Prof. Saathoff, the project leader, are the Danish results crucial for the project and provide a good basis for the development of projects in which clean dredged materials can be applied at sea dikes..

The DredgDikes project will end on 31 January 2015. By then, a guideline with recommendations on the recovery of dredged material in dike construction will be published, and it will also be available through the project website The project with a total budget of more than 2 Million Euro was implemented by a consortium of the University of Rostock and Gdansk University of Technology with the help of three more partners and 15 associated organisations from Denmark, Germany, Poland and Lithuania.

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