The Ports of Stockholm has become one of the first in the world to use a novel method of dredging – freeze dredging – to extend a quay at Frihamnen.
Freeze dredging is performed by lowering large cast iron plates down onto the bottom. To extend the quay, there isa need to go deep and dredge the bottom which enables separation of the upper, more contaminated layer from the underlying purer material without clouding the water.
The plates contain hoses that are filled with a salt solution. This can be cooled to around -30˚C. After two days, the plates are raised again and bring with them around 30cm of frozen bottom material. This can then be used for landfill in as environmentally friendly a way as possible.
Dredging is carried out just outside the Magasin 9 premises at the Frihamnen pier. The quay there will be extended by 80m to make more area available for cruise traffic. The quay will be completed by May 2013.
