Pollution delays cleanup of Swiss munitions dump

The Mitholz ammunition dump is heavily contaminated Keystone / Anthony Anex

An operation to cleanup a World War II ammunition depot in Switzerland will be delayed by two years after unexpectedly high levels of contaminated materiel was discovered.

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Because of the large volume of material with varying levels of contamination at Mitholz in the Bernese Oberland, the cleanup has become more complex. The overall project will take longer with completion now expected in 2047, two years later than previously planned.

On December 19, 1947, part of the 7,000 tonnes of munitions and explosives stored in the facility blew up, killing nine people. The site was considered safe until 2018 when the government ordered it to be cleared of remaining ordinance.

Residents who live near to the depot will have to evacuate the area by the end of 2032 for a 10-year period.

Excavated material can only be reused to a limited extent, and heavily contaminated material must be specially treated.

Preliminary investigations found the area to be contaminated with pollutants. In places, the material is buried several metres deep due to mudslides or later construction work for avalanche protection.

Large quantities of contaminated material were blown into a debris cone in front of the dump by the 1947 explosion. Around 350,000 cubic metres of very heavily polluted material are located there.

Decreased cost

“We have enormous amounts of pollutants in Mitholz and must handle them carefully,” said project manager Adrian Götschi. Crevices and fissures beneath the debris cone could still conceal additional material.

There could potentially be environmental risks, but currently no pollutants have been detected in the water. Only areas around shooting ranges and bullet traps need remediation. Other pasture areas remain safe and can continue to be used for grazing and agriculture.

However, initial work has concluded that the risk of explosion has decreased. The defence ministry can now scale down a protective screen for a railway line, saving about CHF8 million – a small amount compared to the total project cost of around CHF2.5 billion.

Adapted from German by AI/mga

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