On the German federal waterways of the North Sea coast, a standard combination of two dredging techniques has been applied of late: the common dredging method with Trailing Suction Hopper Dredgers (TSHD), and the Water Injection (WI) method.
The WI dredging method is applied in combination with the hopper dredging method to keep the river Elbe at depth. This is required for ensuring safe passage from the North Sea to all harbours along the river Elbe – especially the port of Hamburg. The second largest city of Germany, is home to its main seaport, one of the most prominent ports of Europe.
The ‘Wasser- und Schifffahrtsamt’ in Hamburg, the responsible body for navigational depth of the river Elbe and its tributaries, calls for tenders for maintenance dredging. The specifications include optimising and supporting the efficiency of dredging works with TSHD.
This results not only in economical savings for the German government but also ensures targeting and fast maintenance of the rivers depth at all times.
Following several earlier contracts, Nordsee Nassbagger- und Tiefbau GmbH was again awarded the 12 months dredging campaign between 2015 and 2016. The contract covers a 110 km stretch of the river Elbe between km 638 and km 748, as well as tributaries. This corresponds to the waterway between Cuxhaven and Hamburg.
To guarantee safe passage of shipping traffic to the harbours along the river Elbe and especially to the harbour of Hamburg it is required to maintain the fairway to a depth of 14,40m.
The contract comprises a total of 5.400 dredging hours and 7.400 sailing kilometres between the dredging areas. These are divided in two lots.
Lot 1 is covering the main fairway of the Elbe; lot 2 stands for the tributaries Wischhafener Süderelbe, Glückstädter Nebenelbe, Sperrwerk Tönning, Este and many others which generally can only be dredged during periods of high tide.
One particular feature to be mentioned in this respect is the ferry route between the exposed ferry-ports Wischhafen and Glückstadt, which requires frequent dredging of its very shallow access channels.
As purpose-built control tool and basis of payment, Nordsee Nassbagger- und Tiefbau GmbH developed the software tool “Nordsee Replay.”
The Replay Software allows the contractor and the client to control execution of the works for meeting contract regulations.
By constantly engineering and optimizing DEMEs water-injection dredgers “Dhamra” and “Aligator”, in combination with good communication to the client, the ‘Wasser- und Schifffahrtsamt’ in Hamburg, Nordsee Nassbagger- und Tiefbau GmbH over the past years succeeded in establishing an efficient, flexible and economical working environment.