The Expansion of the Botlek Tank Terminal Area: a Sustainable Solution in the Port of Rotterdam
Type:
Presented during:
WODCON XX: "The Art of Dredging" - 2013, Brussels, Belgium
Authors:
Jumelet HD, Laenen KCJ, Plate SE
Abstract: The ambition of the Rotterdam Port Authority is to expand the Botlek Tank Terminal (BTT) site by reclaiming approximately 5 hectares of land fenced in by a 400 m long quay wall. After completion in mid-2014, BTT will be able to build new oil storage tanks with a total capacity of more than 500,000 m3. To benefit from the practical knowledge of contractors and to achieve the best possible combination between design and construction, the Port of Rotterdam tendered the project as a 'Design & Build' contract. In the call for tenders, tenderers were challenged to come up with innovative solutions for specific design problems, including the anchoring of the quay wall in view of installing the future foundations of the tanks and the method for handling the existing seabed, a silt layer under the new reclamation area etc. The contract for this project was awarded to the joint venture of De Vries & van de Wiel and Geka Bouw.
The existing seabed is covered with a silt layer of maximum 4 metres. The available geotechnical data have been processed and incorporated into a 3D model for determining the thickness of the silt layer. With this technique De Vries & van de Wiel developed a truly sustainable solution: when and where possible, the silt is left in its original location and is only removed where necessary. This allows for keeping the transport of soil to a minimum and for reducing CO2 emissions.
The removed silt is also used as functional fill material for land reclamation. To avoid movement of the silt, it is covered with thinly sprayed layers of sand. The area is divided into different sections, whereby for each section, the consolidation is determined and the optimal combination of vertical drain spacing and surcharge is determined and applied.
During the excavation works, it appeared that the thickness of the silt layer differed slightly from the 3D model. By measuring the exact layer thickness in situ, the required vertical drains and surcharge could be adjusted. Through continuous monitoring (horizontal settlement pipes, levelling rods, etc.) the actual settlement was compared with the predicted settlement. The activities to accelerate the consolidation process were adjusted in order to stay within the allowed remaining settlement. This is an exceptional example of how design and construction are linked together in a sustainable manner.
Keywords: sustainability, settlement, vertical drain spacing and surcharge.