Reassessment of former ammunition depot at Mitholz: Federal Council appoints working group

Bern, 28.06.2018 - The interim report of an expert group has concluded that the risk of another explosion of remnant munitions at the former ammunition depot at Mitholz is higher than previously thought. At its meeting on 27 June 2018, the Federal Council tasked the DDPS with appointing a working group to further assess the risk and propose risk-reducing measures. The interim report concludes that taking immediate measures for the local people is not necessary. Nevertheless, the Federal Council today met with local residents and the authorities concerned to provide them with information.

During World War II, an underground military ammunition depot was built at Mitholz (commune of Kandergrund in the Canton of Bern). In 1947, nine people lost their lives when a series of explosions destroyed some of the 7,000 gross tonnes of ammunition stored in the depot. In the aftermath, only part of the remaining ammunition was cleared away. An estimated 3,500 gross tonnes of ammunition containing several hundred tonnes of explosives remain in the collapsed part of the depot and in a pile of debris outside the facility. Assessments carried out in 1949 and 1986 concluded that the facility could still be used, as any further explosions would only result in minor damage. Based on these assessments, an accommodation facility and an Armed Forces Pharmacy storeroom have remained in use.

New risk assessment comes to different conclusions

At the end of 2017, while planning a new computer centre at the facility, the DDPS commissioned a new risk assessment. A team of external experts from Risk&Safety AG and Bienz, Kummer & Partner AG supported by various specialists from the DDPS carried out the investigation. According to the interim report submitted to the Federal Council, the risk that incidents such as rockslides, a further collapse of the facility or the self-ignition of buried ammunition remnants could lead to an explosion in the buried parts of the facility is higher than anticipated. Any explosion could cause damage to the facility and its close surroundings. The experts anticipate two potential scenarios and have come to the conclusion that the current regulations on handling risks are not being complied with.

Recommendations to be implemented – Federal Council appoints working group

Based on these findings, the experts take the view that there is no need to take immediate measures on behalf of the local people. However, they recommend that measures be devised to reduce the risks. Accordingly, the Federal Council has tasked the DDPS with setting up a working group comprising representatives of all federal departments and the other authorities and agencies concerned. The tasks of this working group, which must be set up by the end of September, include further investigations, such as conducting a geological study, examining specific measures to reduce the risks to the environment, and clarifying the legal consequences.

The interim report's further recommendations pertain exclusively to the DDPS, and are currently being implemented or have already been implemented on the orders of the Head of the DDPS, Federal Councillor Guy Parmelin. This includes closing down the troop accommodation facility and the Armed Forces Pharmacy's storeroom located close to the ammunition remnants, and abandoning the construction project in Mitholz.

Informing the public

The experts will complete their report in the second half of 2018. The DDPS has been tasked with informing the Federal Council about the full report and its recommendations for further action based on the risk assessment. The plan is for the DDPS to submit the report to the Federal Office for the Environment for assessment according to the standard procedure under the Major Accidents Ordinance. Calling in additional experts may be necessary.

Although the assessment is still pending and the interim report does not call for measures to be taken immediately, the Federal Council has already provided the public with information. Federal Councillor Guy Parmelin and the authors of the interim report have already held an information meeting with Mitholz residents and the authorities concerned. Besides the experts' interim report, several historical documents have also been made public for reasons of transparency.

Address for enquiries

Renato Kalbermatten
Head of Information DDPS
+41 58 464 88 75


The Federal Council

General Secretariat DDPS



Federal Office for Civil Protection