"Nessie II" digs deep trenches in the North Sea Mudflats

The "monster" built in Conneforde, Germany, will bury two subsea cables to connect Germany' only offshore oil rig

The subsea cable trencher built in Conneforde weighs 93 tons. In just a few days this self-propelled giant is to bury an 8.5 km long subsea cable 10 meters deep into the mudflats.

Photo: Claus Stölting

Christoffers Kulturbau not only built the 93 ton mega machine, it will also deploy it to bury the cable. The cable will provide the German offshore oil rig "Mittelplate A" with electricity.

By Claus Stölting, Nord-West Zeitung

9 June 2008, CONNEFORDE - In just a few days from now, a subsea cable trencher built by Christoffers Kulturbau GmbH in Conneforde will start working for Germany's only offshore oil rig. The scope of the contract awarded to Christoffers Kulturbau by RWE DEA/Wingas includes burying two 8.5 kilometre long submarine cables from "Mittelplate A" to Friedrichskoog in Schleswig-Holstein. The works must be completed by the end of June, "Because that is when shell duck begin to moult", said the CEO of the company, Hans-Gerd Christoffers. By that time the colossal device built especially for this work must have finished the job and be gone. In the future the cable will supply the offshore oil rig with the electricity so that it can shut down its turbines.

The machine propels itself which is very unusual for its dimensions: the trencher is up to 16.5 metres high and weighs 93 tons. The diesel engine on board of the trencher has 1156 horsepower or 843 Kw. If everything goes well, it should only take 3.5 days for the device to simultaneously dig the 10 metre deep and 36 centimetre wide trench, lay in the cable and immediately refill the trench. In optimal conditions, another 3.5 days will be required to lay the back up cable which must be buried within 15 metres of the main cable. "Nessie II", which followed a smaller model named "Nessie I", operates at low as well as high tide and in 7 metre water depth but when extended  to its maximum height, it can operate as deep as 11.5 metres. The trencher has a maximum length of 24.5 metres, a width of 6.5 metres and is equipped with a 10 metre long, two metre high and two metre wide chain. If the Conneforde based company does its job well, it can look forward to future projects such as laying subsea cables for the offshore wind farms. In a few days, according to Christoffers,  "Nessie II" will be dismantled into three parts and transported to Cuxhaven where it will be loaded onto a boat and shipped to the offshore oil rig to begin its work in the mudflats. Christoffers is optimistic about the success of his "Nessie". The machine will not be serially produced, however, but modified for future jobs. "One Nessie is enough for all of Europe", smiles the entrepreneur.