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Installing a counter fill on the seabed in 2016

In spring 2016, the Norwegian Coastal Administration (NCA) will install a counter fill on the slope by the bow section of U-864 because geotechnical surveys show that the area is highly unstable.

Støttefyllingen skal sikre stabilitet i sjøbunnen rundt forskipet til U-864. (Illustrasjon: Van Oord Norway AS)
Illustration of the counter fill by Van Oord.

 The counter fill is a component of both of the studied alternatives and must be installed regardless of the measure chosen. In spring 2014, the NCA submitted a concept study which evaluated two alternative measures: removing the mercury and then covering the wreck and contaminated area or simply covering the mercury, wreck and contaminated area.

World leading Dutch company awarded contract

A contract has been awarded by the Norwegian Coastal Administration (NCA) through a public procurement process to Van Oord Offshore BV. This Dutch company ranks as a world leader in placing materials on the seabed, and has long experience from similar assignments for the offshore industry in the North Sea.

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.

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.

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.

Established in the deepest part of the wreck area, the counter fill will not affect the choice of later measures to protect the environment. Maritime operations are due to begin in late May 2016 and to last about five weeks.

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