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Stabilising the wreck
Preventing the mercury from spreading further would be no easy task for the NCA. The bow of the wreck had ended up at the edge of a slope. There was a risk that both the bow and the contaminated sediment around it would slide downwards. To prevent this, the NCA called in Van Oord to counter fill the contaminated seabed and to stabilise the wreck. Counter filling is a routine job for Van Oord, but the strict environmental criteria required by the presence of the wreck and the mercury made this project unique.

Toxic cargo
The wreck was discovered by Norway’s Royal Navy near the island of Fedje at 160 metres below sea level. What turned it into a nightmare for the Norwegian Coastal Administration (NCA) was its toxic cargo: 67 tonnes of liquid mercury. It seems that the German sub had been on a secret mission to ally Japan, codenamed ‘Caesar’. It was carrying liquid mercury meant for the munitions industry. The submarine never reached its destination and by the time it was discovered on the seabed, the toxic metal had already spread over an area of 30,000 square metres. 

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play

Watch the project video

Stabilising a 

 Finished project

World War II

Almost 60 years after it was sunk during the Second World War, the wreck of the U-864, a German submarine, was found off the west coast of Norway. Its final journey was on 9 February 1945, when a British submarine fired on it, splitting it in half and sending it to the bottom of the sea. 

submarine wreck 

Hans Petter Mortensholm
Project Manager Norwegian Coastal Administration (NCA)

‘We awarded the contract to Van Oord because of their overall quality and risk-based approach. The NCA is very satisfied with the professionalism displayed by all employees.’

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Specially designed diffuser
Van Oord first installed a layer of sand to reduce erosion and dispersal. To ensure precision at a depth of 160 metres, Van Oord developed a fit-for-purpose diffuser that was then attached to flexible fallpipe vessel Stornes’ remotely operated vehicle (ROV). The vessel installed 30,000 tonnes of sand and then covered this half-metre-thick layer with 160,000 tonnes of rock. This ingenious solution, our thorough risk inventory and our ability to meet the strict environmental criteria convinced the client to partner with Van Oord on this project. 

Project facts & figures

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Extreme precision
Van Oord’s task was to prevent the spread of mercury into the environment. Under the NCA’s requirements, the project team could permit no more than 220 millilitres – a single glassful – of mercury to spread outside the project area. Extreme precision was of vital importance, and measuring and monitoring were essential components of the project execution. A monitoring vessel used environmental and geotechnical measuring equipment installed in and around the project site to monitor vibrations and any movement of the bow.

Maurits den Broeder
Managing Director
Van Oord Offshore

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achtergrond_hout.jpg
o7dd791.png
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bril.png
boat.jpg

Stabilising a 

 Finished project

World War II

Almost 60 years after it was sunk during the Second World War, the wreck of the U-864, a German submarine, was found off the west coast of Norway. Its final journey was on 9 February 1945, when a British submarine fired on it, splitting it in half and sending it to the bottom of the sea. 

submarine wreck 

Toxic cargo
The wreck was discovered by Norway’s Royal Navy near the island of Fedje at 160 metres below sea level. What turned it into a nightmare for the Norwegian Coastal Administration (NCA) was its toxic cargo: 67 tonnes of liquid mercury. It seems that the German sub had been on a secret mission to ally Japan, codenamed ‘Caesar’. It was carrying liquid mercury meant for the munitions industry. The submarine never reached its destination and by the time it was discovered on the seabed, the toxic metal had already spread over an area of 30,000 square metres. 

Maurits den Broeder
Managing Director
Van Oord Offshore

tim.png (copy)

‘Van Oord is determined to play an active role in caring for the planet by guarding the environment. This project is a great example of how we use our Marine ingenuity to do so.’

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Stabilising the wreck
Preventing the mercury from spreading further would be no easy task for the NCA. The bow of the wreck had ended up at the edge of a slope. There was a risk that both the bow and the contaminated sediment around it would slide downwards. To prevent this, the NCA called in Van Oord to counter fill the contaminated seabed and to stabilise the wreck. Counter filling is a routine job for Van Oord, but the strict environmental criteria required by the presence of the wreck and the mercury made this project unique.

Extreme precision
Van Oord’s task was to prevent the spread of mercury into the environment. Under the NCA’s requirements, the project team could permit no more than 220 millilitres – a single glassful – of mercury to spread outside the project area. Extreme precision was of vital importance, and measuring and monitoring were essential components of the project execution. A monitoring vessel used environmental and geotechnical measuring equipment installed in and around the project site to monitor vibrations and any movement of the bow.

Project facts & figures

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160 metres depth

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160,000 tonnes of rock installed

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30,000 tonnes of sand installed

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2 nautical miles west of Fedje Island

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Specially designed diffuser
Van Oord first installed a layer of sand to reduce erosion and dispersal. To ensure precision at a depth of 160 metres, Van Oord developed a fit-for-purpose diffuser that was then attached to flexible fallpipe vessel Stornes’ remotely operated vehicle (ROV). The vessel installed 30,000 tonnes of sand and then covered this half-metre-thick layer with 160,000 tonnes of rock. This ingenious solution, our thorough risk inventory and our ability to meet the strict environmental criteria convinced the client to partner with Van Oord on this project. 

achtergrond2.jpg
btn to top

Hans Petter Mortensholm
Project Manager Norwegian Coastal Administration (NCA)

‘We awarded the contract to Van Oord because of their overall quality and risk-based approach. The NCA is very satisfied with the professionalism displayed by all employees.’

Contact us

About Marine ingenuity is Van Oord’s online magazine. It is published twice a year. Click here to subscribe for the next publication.

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About Marine ingenuity

As a global maritime contractor, Van Oord focuses on dredging, oil & gas infrastructure and offshore wind. Marine ingenuity is Van Oord’s signature and the foundation of our success. It is the spark that lights the spirit of our professionals.
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About Marine ingenuity

As a global maritime contractor, Van Oord focuses on dredging, oil & gas infrastructure and offshore wind. Marine ingenuity is Van Oord’s signature and the foundation of our success. It is the spark that lights the spirit of our professionals.