Dredging Contaminated Sediments in Norway - Exceptional Challenges!

During the last couple of years there has been an increased focus on contaminated sediments in Norway. The main reason for this is that several fjords and harbours have consumption restrictions on fish and shellfish due to contamination. This also has an impact on the fishing industry which is the second largest industry in Norway next to the oil industry. In Norway the contaminated sediments are located in fjords and harbours. Dredging is often the preferred remediation technology to clean up the contaminated sediments. A contaminated sediment layer is often quite thin and additionally the seabed can be very irregular with water depths up to 100 m. These very difficult conditions for dredging has made it necessary to develop specialised dredging equipment. Two types of equipment for environmental dredging have been developed; one for water depths down to approximately 20 m and one for water depths down to approximately 60 m. Both types of equipment are environmental suction dredgers. The dredger which is used down to about 20 m water depth uses a fixed arm and the dredger for larger water depths uses a winch construction. Both types of dredgers are used at the clean-up of the Haakonsvern naval base outside Bergen in Norway.