In the project, the design of the eastern slope has to be aligned over a distance of 1,7 kilometers, which includes the removal of the existing slope protection as well as the deepening of the toe to -17.40m LAT by means of dredging works. The final design will be covered and protected by a new rock revetment. Furthermore, several outlets, amongst others the outfall of Hamburg’s main public water supply facility, have to be modified in the project.
In total, a volume of 370,000 tons of soil, filter material and rocks has to be removed. As the project deploys sustainable methods of construction, the rocks shall be inspected during the dredging process for a beneficial re-use. Remaining rocks and material >10cm shall be disposed at the Kattwyk pier, whilst much finer sediments <10cm have to be brought to the HPA-owned barge unloading dredger at the Finkenwerder Vorhafen. In addition to the reusable rocks, further 80,000 tons of rock material for the filter and armor layers shall be purchased and installed.
The execution of the works takes place with the backhoe dredger HH12 (equipped with a CAT390 Triple) as well as the self-propelled crane barges Steinbutt and Dorsch (equipped with the cable dredger Liebherr LH845 and LH855). These units are designed to work in tidal regimes and in depth of more than 20 meters.
Furthermore, a large fleet of barges, owned by both Boskalis Hirdes and HPA, is required for the transport of not only the dredged material to the different unloading facilities, but also for the supply of purchased materials and the installation of re-used rocks.
In this project, one has to work under tidal influence and consequential strong currents. In addition, there is constant shipping traffic, with huge container vessels, to consider on daily basis. These factors make the overall logistics of the whole Boskalis Hirdes fleet a complicated, always-moving puzzle – and one that the company is most eager to solve satisfactorily.
Execution period: October 2022 – February 2024
