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Former ammunition depot at Mitholz

Ehemaliges Munitionslager Mitholz


The DDPS and the Federal Office of Public Health (FOPH) have commissioned two separate expert reports to assess the situation at the former ammunition depot at Mitholz. Both reports found that there is a higher risk of ammunition remnants exploding than was previously thought. In the summer of 2018, the Federal Council instructed the DDPS to form a working group to address the issue, with representatives from the federal government, the canton of Bern, the communes of Kandergrund and Kandersteg, and the railway company BLS taking part. The working group is charged, in particular, with carrying out extensive technical investigations, evaluating risk reduction measures for the surrounding area, and clarifying emergency and alarm procedures as well as legal issues.

The following measures have been taken to date: in-depth technical investigations of the area’s geology and analyses of individual pieces of ammunition have been conducted. Various devices have been set up in and around the former ammunition depot to measure changes in temperature, gas development and rock movements. Finally, the canton of Bern has developed a corresponding emergency plan.

Clearing the area is the goal

Several remediation options were evaluated last year. As the evaluation concluded that there are negligible differences between the available options, an overall concept for clearing ammunition remnants is now being developed. Based on what we know today, the DDPS expects the actual clearing work to begin in 2031.

As a contingency, should clearing work need to be stopped because of insurmountable problems or because protection goals cannot be met, security can still be increased significantly by covering the area in a layer of rock.

Impact on the population

The clearing work will have effects on the local population and on transport routes between Kandergrund and Kandersteg. Based on current information, residents will have to relocate for ten years or longer while the area is cleared. Furthermore, measures will need to be put in place to protect transport routes.

Support for affected individuals and families

On 25 February, the DDPS held an information event for the residents of Mitholz on the effects of this remediation project. Residents and industry representatives will be involved in the project and will be given the opportunity to share their views on the issue.

The DDPS will make itself available to those affected, and will offer residents whatever support they need, in particular while they prepare to relocate.

The DDPS will update the persons affected and the authorities on an ongoing basis. At the request of the communal authorities, since December 2018 the DDPS has also been publishing a newsletter with information on the work being done.

Former ammunition depot in Mitholz

During World War II, an underground military ammunition depot was built at Mitholz in the commune of Kandergrund, Bern. In 1947, part of the approximately 7,000 gross tonnes of ammunition stored exploded, killing nine people. Part of the remaining, unexploded ammunition was cleared out. According to estimates, up to 3,500 gross tonnes of ammunition containing several hundred tonnes of explosives remain in the collapsed parts of the depot and in the large pile of rubble in front of it. Earlier assessments in 1949 and 1986 both concluded that, although further explosions could not be ruled out completely, any possible further damage would be limited to the facility itself, and that the depot could continue to be used. In 1948, clearing away the remaining ammunition remnants was considered too high a risk, primarily for geological reasons.