The Norwegian Coastal Administration (Kystverket) has investigated how best to mitigate the environmental risk posed by the “U-864” and its mercury cargo. Two options were considered: first recovering the mercury containers from the wreck and then covering them, or securing the wreck, together with its cargo and the already contaminated surrounding area, directly by covering it.
Full coverage recommended
Kystverket recommends the second option. Both options would significantly reduce the long-term environmental risk, according to the Official statement on the report concerning U-864. However, the recovery of the cargo is said to be more difficult to carry out, poses a greater risk of mercury being released and incurs significantly higher costs.
Mercury is already present in the water
According to the latest findings, remotely operated underwater vehicles could reach the keel boxes of the wreck and retrieve the mercury containers. However, not only intact steel containers were found, but also some that had already been damaged by corrosion. In addition, free-floating mercury has already been detected in the bilge and on the seabed around the wreck.
That is precisely where the problem lies: work on or in the immediate vicinity of the wreck could stir up contaminated sediment and spread mercury throughout the area. By contrast, the updated assessment of the risk posed by munitions is comparatively reassuring. A detonation is considered unlikely under the planned measures, provided the wreck is not subjected to significant mechanical stress.
The British were well aware
“U-864” was a Type IX D2 submarine designed for long-range operations. On 9 February 1945, it was sunk off the port of Fedje in western Norway by the submarine HMS “Venturer”. The British were aware of the planned German operation through their intelligence services.
All 73 people on board lost their lives. The wreck, discovered in 2003, lies at a depth of around 150 metres and was broken into two main sections by the torpedo strike amidships. On board was a large quantity of mercury in steel containers, which was en route to Japan.
The Background information on mercury and ‘U-864’ show why the situation is being monitored so closely: under certain conditions, the heavy metal can be converted into particularly toxic methylmercury and enter the food chain via soil organisms.
Stress as a long-term problem
A recent report by the German Press Agency on mercury in the North Sea highlights just how persistent this pollution can be. According to the report, at almost half of the monitoring sites examined in the coastal North Sea, the threshold value of 0.15 milligrams per kilogram of sediment – set by the OSPAR coastal states – was exceeded. Sediments near river estuaries are particularly affected.
Mercury binds to soil sediments and hardly breaks down at all. It therefore remains a concern even in areas where direct inputs have declined. The Federal Environment Agency also points out that the atmospheric mercury inputs into the North Sea Although they have fallen significantly since 1990, this does not solve the problem of contaminated sites where sediments are already polluted.
Minimising the risk posed by “U-864”
Based on investigations carried out to date, Kystverket has not yet reported any higher levels of mercury in fish and shellfish in the waters off Fedje than in other parts of the west Norwegian coast. However, as the risk of long-term contamination posed by “U-864” is significant, action is now to be taken in good time.
In German mining areas, too, debates are taking place about the Dealing with hazardous sites contaminated by munitions and, more generally, about the industrial use of the North Sea, that the issue is of great importance.
Do you think covering a contaminated wreck is the more convincing solution – or should Norway still recover the mercury containers, provided this is technically feasible?