Explosion disaster in Mitholz

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The collapsed Fluh and the devastated village of Mitholz in January 1948

The Mitholz disaster was a series of heavy explosions on December 19 and 20, 1947 in an ammunition dump of the Swiss Army above Mitholz in the municipality of Kandergrund in Switzerland . The disaster was one of the largest man-made explosions that were not caused by nuclear weapons .

The destroyed village center

Nine people were killed in the explosions and seven others were injured. Large parts of the nearby village of Mitholz were devastated, several residential buildings and the Blausee-Mitholz station of the Lötschbergbahn were destroyed.

The facility was then partially rebuilt and used as a camp and troop accommodation. In 2018, however, the authorities found that the remains of ammunition in the facility still pose a risk of explosion. The ammunition store is therefore to be completely cleared from 2031. This should cost around one billion francs and mean that Mitholz will be evacuated for over ten years.

Starting position

Plan of the ammunition depot

The Bäuert Blausee-Mitholz is 962  m above sea level. M. in a narrow valley floor surrounded by steep rocks in the Kandertal in the Bernese Oberland . The village is crossed by the Frutigen – Kandersteg state road and by the Lötschberg mountain route in a large loop. On December 19, 1947, 227 people were present in Blausee-Mitholz.

The Fluh around 1930, before the camp was built

On October 1, 1940, the Federal Building Department commissioned a project for an underground ammunition storage facility in Kandertal. After various geological reports, the Fluh in Mitholz was chosen as the location , a conspicuous rock head with a practically vertical wall about 200 m long and 50-100 m high. Originally, six ammunition chambers were planned, each 100 m long and 8.5 m wide, but shortly after construction began in 1941, the War Material Administration gave the order to extend them to 150 m. The chambers ended on one side in a loading tunnel in which there was a siding to the nearby Blausee-Mitholz station of the BLS . The loading tunnel was also accessible for trucks through two gates. At the rear end, the ammunition chambers were connected to one another by a tunnel. In one of the engine rooms there was an emergency power system with diesel generators, which also temporarily supplied the BKW network when there was a lack of electricity . Outside the underground facility there was a keeper's house and other buildings. The ammunition depot was provisionally removed in 1944 and handed over to the War Material Administration; in 1945 the project was completed. At the time of the accident, there were around 7,000 tons of mixed ammunition in the warehouse, which at the time was considered to be one of the most modern of its kind in Switzerland.

Explosion of an ammunition dump at Fort Dailly

On May 28, 1946, 449 tons of ammunition exploded in the fortress Dailly near Saint-Maurice , killing ten workers and destroying large parts of the fortress. This disaster, which was the first of its kind in Switzerland, put the safety of the large, centralized ammunition depots built up until then into question. As a result, a sub-commission for ammunition storage was set up with the task of examining the safety of the ammunition storage facility and working out measures to improve it. At the time of the explosion in Mitholz, the work of the sub-commission had not yet been completed, and the measures that had been decided by then had only been partially implemented. Also in the depot of Mitholz worked on the day before the accident armory -arbeiter mind that when bullets fuse unscrew and store separately.

Course of the accident

Damaged infrastructure in Mitholz station, smoke is still emerging from the rubble of the ammunition dump

On December 19, 1947 at around 11 p.m. flashes of light and flames were observed emerging from the access tunnel. A short time later, residents were woken up by loud noises reminiscent of the fall of avalanches . At 11:30 p.m., the first large explosion occurred in which up to 30 m high flames shot from all entrances. The northern armored gate was blown off and smashed the station building .

Five minutes later there was a second, more powerful detonation, which was registered 115 km away by the Swiss Seismological Service in Zurich. Thrown ammunition and debris destroyed several buildings. Ten minutes after midnight there was the third and most violent explosion, accompanied by 150 m high flames. The rock face in which the ammunition depot was located collapsed, with about 250,000 m³ of rock loosening. Boulders weighing tons were hurled hundreds of meters away, an aerial bomb even covered a distance of two kilometers. Debris, splinters and partly burning ammunition remnants were distributed over a wide area.

During the night and the following day there were repeated detonations and fires. Smaller explosions were observed on December 28th. Around 3,000 of the 7,000 tons of ammunition in storage exploded or burned. Some of the residents of Mitholz fled their homes in only underwear and coats. Some took refuge in a railway tunnel . The fire brigade collected the fleeing people and placed them in inns.

root cause

Exploration of the flooded rear connecting passage

The cause of the explosion is not exactly clear. It is believed that a chemical reaction in a detonator caused a self-triggering, which started a chain reaction. The formation of a highly explosive copper-nitrogen compound, which is favored by even slight friction or vibration, was assumed to be the most likely cause in the report of the investigative commission.

follow

The completely destroyed station building Blausee-Mitholz

Nine people were killed, including at least three children.

damage

Over 40 houses were damaged, 20 of which had to be rebuilt. According to estimates, the total damage amounted to around 100 million francs, which today corresponds to 490 million francs. The Lötschberg mountain route was closed until December 28th. The railway bridge over the cantonal road was destroyed, the station building and the tracks of Blausee-Mitholz were covered by rubble, whereby the station director and his son were killed. The clean-up was difficult because live ammunition was scattered all over the valley and covered in snow.

The residents of the destroyed houses stayed with relatives or in makeshift barracks . The reconstruction of Mitholz was therefore soon tackled under great time pressure. Carpenters from the Frutigtal rebuilt twenty houses in the timber construction typical of the valley, with advice from the Bernese Heimatschutz (Homeland Security) . At the end of 1948, 13 of the newly built houses were already inhabited. Many of the houses in Mitholz have house sayings that are reminiscent of the misfortune.

1948 newly built house with a motto reminding of the catastrophe

"A horror ran through the whole country
When our village was destroyed, burned
Now the joy has returned
As we have a new one"

- House motto in Mitholz

reaction

The day after the disaster, the Tages-Anzeiger published a report calling for help for the affected population. In the days that followed, a large number of packages with clothes, shoes and other relief supplies arrived. Furthermore, at least CHF 120,000 were donated, of which Fr. were of the 80,000 Swiss Solidarity collected. Henri Guisan and Federal Councilor Karl Kobelt visited the accident site, among others .

Continue

During the explosion, a large part of the 100 m high Fluh collapsed, which is still clearly visible

After the disaster, the Swiss Reinsurance Company announced that the Swiss insurance companies were no longer able to insure Swiss ammunition depots under the so-called federal police . In order to counter the dangers posed by outdated ammunition stocks, the Federal Council decided on March 16, 1948 that 2,500 tons of artillery ammunition should be sunk in Lake Thun , Lake Brienz and Lake Lucerne . In addition, around 1500 tons of residues from Mitholz were sunk in Lake Thun. The accidents at Dailly and Mitholz led to the disposal of old ammunition under great pressure from the public. A quick and safe solution was therefore required, but ecological concerns were neglected and the disposal operations were only inaccurately documented.

The plant after 1947

Warehouse for medical supplies from the army pharmacy in Mitholz

Reconstruction and use as a warehouse

As early as the summer of 1948, the Federal Building Department began studies and preparatory work for the reconstruction of the facility in Mitholz. The further storage of ammunition was out of the question; instead, the project envisaged an underground material store, the storage rooms of which would also be made available to other departments of the army.

Construction work began in the autumn of 1953, during which, among other things, a new access tunnel was created that crosses all six chambers and divides them in the middle. In the years that followed, the Federal War Material Administration changed the requirements for the new facility several times, until construction work was temporarily suspended in 1958.

In 1961, the federal government finally granted a loan of 23 million francs for the construction of a large underground hospital with an attached hospital and war pharmacy, which was also supposed to accommodate serious surgical cases. Construction began in 1962. In the course of the construction work, however, the project of a large, central military hospital turned out to be outdated. For this reason, the Federal Council decided in 1971 to stop the construction work again.

The tunnels were then used by the army pharmacy as an external storage facility with a manufacturing facility and received troop accommodation for 100 people.

New risk assessment 2018

June 2018: Federal Councilor Guy Parmelin visits the facility with Melchior Stoller

As part of the planning for a new data center , the DDPS commissioned a new risk assessment for the remaining ammunition residues in Mitholz at the end of 2017 . The Federal Council announced the preliminary results on June 28, 2018. In contrast to earlier investigations in 1948 and 1986, the commissioned group of experts found that the plant still posed an impermissibly high risk.

According to their estimates, there are still around 3,500 tons of ammunition with several hundred tons of explosives in the collapsed parts of the facility and in the debris cone in front of it. Parts of the ammunition are concentrated in larger accumulations, which leads to places with a high density of explosives. Influences such as rock falls, lightning strikes , sabotage or self-ignition of the ammunition could continue to lead to explosions. The probability of a smaller explosion with one tonne of TNT equivalent is therefore one event every 300 years, that of a larger explosion with 10 tons one every 3000 years.

Since these risks exceed the permissible limit values ​​in some cases massively, the DDPS had the troop accommodation vacated immediately. The warehouse of the army pharmacy, which would have been taken out of service as planned by the end of 2019, was shut down early. The plans for the new data center were also waived. For the population of Mitholz, immediate measures such as an evacuation or the blocking of roads and railway lines were not considered necessary.

The federal authorities formed a working group to examine the situation more closely and work out measures to contain the risk. In September 2019, she published a report. In June 2019, 62 sensors and thermal imaging cameras were installed in the facility for monitoring purposes. In the event of renewed explosions, an evacuation concept recommended the establishment of protective cellars for the population of the Kandergrund community .

The Mitholz facility was removed from the list of military facilities on June 25, 2018 and has no longer been subject to confidentiality .

In March 2021 it became publicly known that traces of trinitrotoluene (TNT) from the ammunition store in Stegenbach, the Kander , Lake Thun and in the groundwater had already been detected in 2018 . Because of the low concentrations, the DDPS refrained from informing the public about it.

Planned evacuation of the facility and evacuation of the village from 2031

On February 25, 2020, the DDPS announced that the canton of Bern and the affected communities of Kandergrund and Kandersteg intended to completely clear the ammunition residues in the former ammunition store. After extensive preparatory work, the clearing work is to begin in 2031. The population of Mitholz, around 50 households with 170 people, is expected to live elsewhere for an estimated ten years during the eviction. The estimated cost is over a billion francs. A report by ETH Zurich published on August 25, 2021 concluded that the evacuation of the population was inevitable. The safety of the population was not guaranteed with a concept of encapsulation of the ammunition residues that civil engineering experts had brought into play.

Similar events

After the Second World War , accidents in ammunition depots increased in Switzerland. In Fort Dailly 1946 ten workers died in an explosion. In the case of minor incidents in Ruis in Graubünden and central Switzerland, no people were injured. An ammunition magazine burned down in Göschenen in 1948.

On November 2, 1992 on the Susten Pass, 225 to 840 t of ammunition and 279 solid fuel boosters from Bristol Bloodhound anti-aircraft missiles detonated in an ammunition destruction facility near the Steingletscher . Six people were killed.

Web links

Commons : Mitholz Explosion Disaster  - Collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d Valentin Gitermann: On the explosions by Dailly and Blausee-Mitholz . In: Social Democratic Party of Switzerland (ed.): Red Review: socialist monthly . tape 27 , no. 4 , 1948, pp. 146–155 , doi : 10.5169 / seals-335975 .
  2. ↑ Police Corps of the Canton of Bern: 1. Preliminary report on the explosion disaster in Mitholz . Frutigen December 21, 1947, State Archives of the Canton of Bern: BB January 14, 408, p. 11–21 ( be.ch [accessed December 4, 2017]).
  3. ↑ Ingenieurbureau Dr. Hans Fehlmann: Chronological building history of the underground magazine Blausee-Mitholz . Bern January 16, 1948, Swiss Federal Archives: E5150A # 2008/190 # 63 * ( admin.ch [accessed on March 17, 2020]).
  4. ↑ a b c d e Hansjörg Rytz, Khosrow Bakhtar: Analysis and Documentation of the Mitholz Underground Ammunition Storage Accidental Explosion in Switzerland . In: Proceedings of the Twenty-Seventh DoD Explosives Safety Seminar Held in Las Vegas, NV on August 22-26, 1996 . Las Vegas, Nevada 1996 (English, dtic.mil ).
  5. ^ Report of the Swiss Federal Council on its management in 1950 . In: Annual reports of the Federal Council . tape  96 , 1950, 50 000 317, pp. 221–229 ( admin.ch [PDF; accessed December 4, 2017]).
  6. ^ Federal War Material Administration: Report of the Sub-Commission for Ammunition Storage of February 28, 1948 . Bern February 28, 1948, Swiss Federal Archives: E5150A # 2008/190 # 56 * ( admin.ch [accessed on March 17, 2020]).
  7. ↑ a b c d Eduard Kleinjenni: Mayor Eduard Kleinjenni reports on the explosion in Mitholz from 19./20. December 1947 . Ed .: Municipality of Kandergrund. ( kandergrund.ch [PDF]).
  8. ↑ Pascal Kupper: «There was no alternative to sinking». In: jungfrauzeitung.ch . Gossweiler Media AG, April 17, 2011, accessed on July 9, 2017 .
  9. ↑ a b c Swiss Accident Insurance Fund (Ed.): Results of the accident statistics for the sixth five-year observation period 1943–1947 . S. 24 ( unfallstatistik.ch [PDF]).
  10. ↑ This figure was calculated automatically , has been rounded to the nearest million francs and relates to January 2021.
  11. ↑ Patrick Belloncle, Rolf Grossenbacher, Christian Müller, Peter Willen: The big book of the Lötschbergbahn . The BLS and its co-operated railways SEZ, GBS, BN. Edition Viafer, Kerzers 2005, ISBN 3-9522494-1-6 , p. 153-154 .
  12. ↑ Reconstruction of the village of Mitholz in the Kandertal . In: Schweizerische Bauzeitung . tape  67 , no. 18 . Verlag AG of the academic technical associations, April 30, 1949, p. 249-250 , doi : 10.5169 / seals-84049 .
  13. ↑ Prof. Dr. Walter Rohrbeck: Cross section through insurance research . In: Series of publications by the Institute for Insurance Science at the University of Cologne . Duncker & Humblot, Berlin and Munich 1949, p. 183 .
  14. ↑ Federal Department of Defense, Civil Protection and Sport DDPS (ed.): Historical investigations into deposits and ammunition dumping in Swiss lakes - summary . Bern November 5, 2004, p. 2–3 ( admin.ch [PDF]).
  15. ↑ Radioactive Waste Management Committee, OECD Nuclear Energy Agency (Ed.): Loss of Information, Records, Knowledge and Memory - Key Factors in the History of Conventional Waste Disposal . March 26, 2014, JT03355066, p. 33–34 (English, oecd-nea.org [PDF]).
  16. ↑ Directorate of Federal Buildings: Blausee-Mitholz underground facility . Bern March 3, 1960, Swiss Federal Archives: E3001B # 1978/31 # 188 * ( admin.ch [accessed on March 17, 2020]).
  17. ↑ SR eighth meeting of 09.28.1961 . In: Minutes of the Federal Assembly . tape  36 , no. 08 . Bern September 28, 1961, 100005776, p. 155–161 ( admin.ch [PDF; accessed July 3, 2018]).
  18. ^ Military buildings and land acquisitions . In: Official Bulletin of the Federal Assembly . tape  III , no. 08 . Bern September 29, 1976, 20005079, p. 1083–1093 ( admin.ch [PDF; accessed on July 3, 2018]).
  19. ^ A b c Peter Kummer, Peter Nussbaumer: Risk assessment 1051 AA: Interim report of the expert group . Ed .: Federal Department of Defense, Civil Protection and Sport DDPS. April 27, 2018 ( admin.ch [PDF; accessed July 3, 2018]).
  20. ↑ a b c reassessment of the former Mitholz ammunition depot. Federal Department of Defense, Civil Protection and Sport DDPS, accessed on July 3, 2018 .
  21. ↑ a b Risk of explosion in the former Mitholz ammunition depot. Swiss radio and television , June 28, 2018, accessed on July 3, 2018 .
  22. ↑ DDPS, communication defense: evacuation will take place faster than originally planned. Federal Department of Defense, Civil Protection and Sport DDPS, July 2, 2018, accessed on July 4, 2018 .
  23. ↑ a b Federal Department of Defense, Civil Protection and Sport DDPS: Former Mitholz Ammunition Storage - Status Report of the Mitholz Working Group. (PDF; 156 KB) In: admin.ch . September 30, 2019. Retrieved October 29, 2019 .
  24. ↑ Eyes on the former Mitholz ammunition depot. Der Bund , December 5, 2018, accessed on December 6, 2018 .
  25. ↑ Matthias Thomi: Mitholz ammunition store - traces of explosives from Mitholz found in the water. Swiss Radio and Television (SRF), March 1, 2021, accessed on March 1, 2021 .
  26. ↑ Results of the water tests in Mitholz are available. DDPS General Secretariat, Defense Group, armasuisse, March 1, 2021, accessed on March 1, 2021 .
  27. ^ Clearance of the former Mitholz ammunition dump: start of participation for the population , notification from the DDPS dated February 25, 2020
  28. ↑ Mitholz ammunition store: The whole village has to move for 10 years , SRF, February 25, 2020
  29. ↑ Because of spilled ammunition: The population of Mitholz is to move away for ten years In: Neue Zürcher Zeitung of February 25, 2020
  30. ↑ The evacuation of the mountain village Mitholz is inevitable: an ETH report destroys the last hope , Neue Zürcher Zeitung, 25 August 2021.
  31. ↑ Hans Urfer: The memories of the tragedy are omnipresent. In: bernerzeitung.ch . Tamedia AG, November 1, 2012, accessed on July 11, 2017 .

Coordinates: 46 ° 31 '32.1 "  N , 7 ° 40' 44.5"  E ; CH1903:  618 444  /  152725