Dredged silt goes to Rotterdam
Hopper dredger ‘Hein’ dredges the first load of silt for Rotterdam in front of the Lloyd shipyard in Bremerhaven.
The crunch of environmental concerns and filling dump facilities has meant large quantities of sediment from the harbours in Bremerhaven will soon set off on a journey abroad.
The port management company Bremenports has signed a contract for the disposal of harbour sediment with its partner organisation Hafenbedrijf Rotterdam.
Over a period of eight weeks, the hopper dredger Hein will remove some 60,000 cu/m of silt from the bottom of Überseehafen in Bremerhaven and take it to the Dutch port of Rotterdam, where the silt will be deposited in 'De Slufter', an underwater confined disposal facility south of the approach to the port of Rotterdam.
The project is scheduled for completion by the beginning of March. Dr Stefan Woltering, managing director of Bremenports explainsed, ‘In recent years, Bremenports has built up excellent contacts with the management of the Port of Rotterdam. Disposal of the harbour sediment in De Slufter is now a direct benefit of these connections.’
The greatest quantities of sediment occur behind the locks in Bremerhaven. To compensate for declining water levels caused when seagoing vessels pass through the locks, water from the Weser, which contains suspended matter, regularly has to be pumped into the harbour.
In contrast to the sand from the mooring basins at the Container Terminal, the harbour sediment contains contaminants. Since 1997, it has no longer been permitted to dump such sediment in the Wurster Arm, the old fairway in the Outer Weser. Since then, the sediment has been taken to a special disposal facility for dredged material in Bremen.
Over the past few years, substantial quantities of silt from Bremerhaven have been taken to the Lower Rhine, where they were used for the reclamation of abandoned gravel pits. The new cooperation with Rotterdam now offers an alternative disposal option.
Refered to as a ‘subaquatic confined disposal facility, De Slufter can hold approximately 150m cu/m of silt. According to the operators, 75m cu/m of dredged material have already been deposited there.
The De Slufter disposal facility consists of a pit which is up to 28m deep and enclosed by a 24m high ring dyke. Above the waterline, the dyke has a 1m thick sealing layer of clay on the side facing the disposal site. The dredged material arrives by hopper dredger or barge and is pumped into De Slufter through a floating pipeline. The facility was originally approved for the disposal of contaminated dredged material in Dutch Classes 2 and 3. In 2000, the licence was modified and it has been approved for more severely contaminated Class 4 material since then.
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