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U-864: Dutch company to install counter filling

The Norwegian Coastal Administration (NCA) has awarded a contract to Van Oord Norway AS for counter filling in the wreck area for the submarine U-864, outside the island of Fedje on the west coast of Norway.

Støttefyllingen skal sikre stabilitet i sjøbunnen rundt forskipet til U-864. (Illustrasjon: Van Oord Norway AS)
Støttefyllingen skal sikre stabilitet i sjøbunnen rundt forskipet til U-864. (Illustrasjon: Van Oord Norway AS)

Intended to ensure seabed stability in the area, this operation must be conducted regardless of the main measure chosen to protect the environment against mercury pollution from the German World War Two wreck.

 World leading company

This Dutch company ranks one of the world leaders in installing counter fills and other advanced rock installations at sea beds and has long experience from similar assignments for the offshore industry in the North Sea.

Monitoring the environment

Stringent requirements have been set for environmental monitoring of the work. Such checks will be conducted during the maritime operations by the Norwegian Institute for Water Research (Niva) as a subcontractor to Van Oord.

   “Following a detailed evaluation, Van Oord was found to have submitted the best overall tender,” says Johan Marius Ly, director of emergency preparedness at the NCA.

 Unstable seabed

New geotechnical analyses of the seabed in the area around the Second World War wreck were conducted in 2013. On that basis, experts from the Norwegian Geotechnical Institute (NGI) and DNV GL recommended that counter filling should begin as soon as possible.

Controlled operation

This operation involves laying some 100 000 cubic metres of sand and rock in a controlled and precise manner from a specially designed ship in order to stabilise the seabed.

   "That in turn will reduce the risk of movement by unconsolidated sediments, including materials contaminated with mercury leaked from the submarine," Ly concludes.

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 Established in the deepest part of the wreck area, the counter fill will not affect the choice of later measures to protect the environment.

Facts

  •  Van Oord awarded contract for installing counter filling beside the forepart of the wreck.
  • The counter filling is intended to ensure seabed stability in the area.
  • Maritime operations are due to begin in late May 2016 and to last about five weeks.
  • A preliminary project commissioned by the Norwegian Ministry of Transport and Communications was submitted by NCA in May 2014. This detailed two options – either removing mercury containers from the hull with subsequent coverage of the wreck and polluted sediments, or simply covering the wreckage and the contaminated seabed.

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