Dumped munitions in Lake Thun must go

Some 70 per cent of white fish in Lake Thun suffer from abnormalities Keystone Archive

Munitions dumped by the Swiss army in Lake Thun must be removed and disposed of, says the Bernese cantonal fishery association.

The weapons jettisoned during the last century are suspected of causing deformities in white fish on an unprecedented scale in this body of water, located in canton Bern.

The fishery association issued the call after discussing ways of extracting the munitions during its annual general meeting this week.

One proposal from a consortium of three German companies proposed freezing the motley assortment before removal as blocks of ice.

After extraction, the ice blocks would be stored in secure, cooled facilities until they could be finally disposed off.

Claus Mayer from one of the companies, Nordseetaucher, explained that ice had a compression strength similar to concrete, making it a safe material to use.

Survey

However, Mayer explained that before the weapons could be raised, it would be necessary to take a closer look at what kind of munitions were involved.

This would require the use of a mini-submarine to explore the lake’s bed. What is known is that the dump lies more than 200 metres deep and is covered by a layer of sediment around 25 centimetres thick.

Mayer estimated that the mini-submarine would have to be used over 160 days to map the area concerned, at a daily cost of about SFr23,000 ($18,314).

Altogether 3,000 tons of ammunition were dumped in the lake between 1940 and 1963, including shells, fuses, and large bombs.

Danger

Alarm bells first rang in 2000 when the Bern’s fishery department discovered deformities in white fish in Lake Thun, particularly in their reproductive organs.

Up to 70 per cent of the fish are affected and no one can say with any certainty why Lake Thun has been affected to this extent.

One theory is that the munitions might have started to leak.

Another is that blasting in the nearby Kander Valley – which began in 1999 – to create new transalpine tunnels might also be to blame.

Linking both scenarios is the explosive, TNT, which could be polluting the waters.

Last year canton Bern began a five-year-study to pinpoint the cause of the problem.

Officials maintain that the water is perfectly safe to drink and that the fish are safe to eat.

swissinfo with agencies

In brief

The fishery association has called for munitions dumped by the Swiss army to be removed from Lake Thun.

It suspects that the weapons are responsible for causing deformities in the lake’s white fish.

It has suggested at least one method of disposing of the munitions.

Key facts

The Swiss army dumped munitions in Lake Thun between 1940 and 1963.
The dump lies more than 200 metres deep.
Deformities in the lake’s white fish were first acknowledged in 2000.