Dethlinger pond

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The Dethlinger pond (May 2019)
Warning sign at the edge of the pond

The Dethlinger pond is a former diatomaceous -Grube in the during and after World War II explosives and chemical weapons were sunk in nationwide unprecedented amounts.

location and size

The Dethlinger pond is located approx. 3 km southeast of Munster (Örtze) and approx. 1 km northeast of Dethlingen, a district of Munster. At this location, the United Deutsche Kieselgurwerke GmbH mined kieselguhr in open-cast mining until around 1926. Rainwater created a pond. The pit has a maximum size of about 60 meters in diameter. According to recent studies, the actual depth of the former kieselguhr pit is around 9 m. Geophysical measurements in the 1980s showed a depth of up to 21 m. The possible volume of pollutants is therefore lower than feared in the past. The OHE railway line Beckedorf – Munster and the federal road 71 run in the immediate vicinity of the mine . At the end of 1996, the administrative responsibility for the old armaments site Dethlinger Teich changed from the state of Lower Saxony to the then district of Soltau-Fallingbostel, now the district of Heidekreis . The property is still privately owned.

history

Air Force Main Ammunition Plant

Just east of Dethlinger pond was in 1935, during the Nazi era , as part of the upgrade of the Armed Forces , the Air Force main ammunition institution 4 / XI Oerrel (colloquially "Muna" ) built. She was subordinate to Luftzeuggruppe XI Hannover. The facility consisted of more than 150 buildings and bunkers. The concrete bunkers were 40 x 25 m in size, were covered with earth for camouflage and were hidden in the forest. Warfare ammunition for the Air Force was filled and stored here . Incendiary bombs were also manufactured from 1941 and chemical weapons from 1942 . The warfare agents were delivered by rail in tank cars. The highly contaminated wastewater, most of which arose from cleaning the tank wagons, was disposed of in the Dethlinger pond after being passed through three infiltration ponds.

Backfilling and securing the pit

100 mm groundwater measuring point

In April 1945 the British Army took over the Muna grounds with all the warfare agents still there without a fight. The transportable part of the ammunition was scuttled and dumped in the North and Baltic Seas during Operation Davy Jones' Locker . The part that could not be transported and the still unfilled warfare agent was sunk in the Dethlinger pond. The Hanover police bomb clearance command , founded in 1948 as a bomb clearance command for the state of Lower Saxony, used the mine until 1952 for the disposal of warfare ammunition. From the beginning of the 1950s, residents took ammunition parts containing non-ferrous metal out of the mine at considerable risk in order to sell them to scrap dealers. In response to this, in 1952 the pond was filled with rubble from the former bunkers of the Muna and covered with earth. However, the responsible authorities feared even then that the groundwater could be endangered by the warfare agents. In 1957 the first four measuring points were built. On behalf of the water management office in Celle and Verden , 16 further measuring points were set up in stages from 1975. In 1999 the so-called “sloping well” and seven other groundwater measuring points were built.

Contents of the pit

There is great uncertainty about the amount of ammunition actually sunk. Any written documents or counting lists do not exist. The information comes from contemporary witnesses, was estimated and is therefore inaccurate.

Quotation of the Lower Saxony state government 2014 on a small request :

“ The multitude of possible substances and their chemical behavior, including among themselves, do not currently allow a serious description of the pond content. "

To be appreciated:

  • approx. 100,000 pieces. Type C-98 primer charges
  • approx. 3000 pcs. Warfare grenades , 7.5 cm to 32 cm caliber
  • approx. 150 pcs. Warfare ammunition 7.5 cm to 15 cm
  • approx. 200 - 300 phosgene bombs with filling, defused (approx. 100 kg each)
  • approx. 300 barrels with 250 l liquid phosgene each
  • approx. 100 barrels each with approx. 100 l Lost

Redevelopment

Pond opening

Control wells and measuring stations

With the help of the groundwater measuring points set up, the Helmholtz Center for Environmental Research - UFZ determined the groundwater levels and the groundwater inflow in mid-October 2015 . A scoop sample in the pond area showed that the groundwater was clearly contaminated with polycyclic aromatic hydrocarbons (PAHs) and decomposition products of the warfare agent mustard. Pollutants have also been found outside of the pit area. In spring 2018, the chemical agent Clark I was detected at a measuring point for the first time . A so-called “pond opening” is necessary for the planned renovation . This should be done at a point where there is a high probability of warfare ammunition. The type, quantity and condition of the pit contents should be determined. The result then forms the basis for the renovation. The preliminary examination is also mandatory for applying for grant funds. The work group Mull & Partner Ingenieurgesellschaft mbH - Hazard Control GmbH will carry out the work. The state of Lower Saxony will contribute a maximum of two million euros to the costs by 2020. The opening of the pond was originally planned for the winter of 2017/2018. In the period from September 16, 2019 to probably the end of April 2020, the district of Heidekreis will now take the necessary samples (originally the campaign should be completed by December 20, 2019). For this purpose, a lightweight hall with negative pressure and air extraction / treatment has been set up above a shaft. It contains an access lock for personnel and material and a lock for docking transport / storage containers. Warfare grenades that are recovered during the exploration work are delivered to the Society for the Disposal of Chemical Warfare Materials and Old Armaments mbH (GEKA mbH) in Munster, examined here and destroyed in their incineration plant.
During the work on Dethlinger Teich, the B 71 from Dethlingen to Oerrel will be completely closed (probably until the end of April 2020).

Pond opening timeline

  • September 16 to 20, 2019 - familiarization of those involved
  • September 27, 2019 - Start of the removal of the surface layer applied in 1952
  • October 8, 2019 - First ammunition found
  • December 29, 2019 - The work will resume on January 7th after a Christmas break. The B71 will be fully closed again until April 30, 2020. It will be opened to traffic from December 21, 2019 to January 6, 2020.
  • January 21, 2020 - exploration work resumes. Since the dewatering did not work, another exploratory shaft (shaft II) is being sunk.
  • February 10, 2020 - work on shaft I will continue after the swamp
  • February 25, 2020 - all grenades recovered so far were without detonators. Only a few grenades were leaking. Lost was always detected in these grenades. 100 m³ of water are used daily. A groundwater purification system (GWRA) is required to continue working. The award procedure for this is being prepared.
  • February 28, 2020 - Shafts I and II have reached the water table; Without a GWRA, work cannot continue. A third shaft is planned.

Salvaged ammunition

Total number of ammunition recovered
date Type number comment
08 October 2019 0.001
October 10, 2019 0.003 Shaft I is 1.7 m deep
October 14, 2019 10.5 cm and 15 cm caliber artillery shells 0.008th all grenades were not ignited
October 28, 2019 0.100 Shaft I is 2.2 m deep
22nd November 2019 0.760 Shaft I is 2.7 m deep. The ammunition comes from approx. 12 m³ of excavated material
November 28, 2019 1.006
December 05, 2019 1.106
19th December 2019 1,401
February 06, 2020 1,621 Shaft I is approx. 4.5 m deep
February 14, 2020 1,842
February 27, 2020 2,552 Shaft I is approx. 4.6 m deep, shaft II approx. 4.1 m deep
March 26, 2020 So far recovered: 33 tons of ammunition, 2.8 tons of chemical filling, 780 kg of explosives

Proven environmental toxins

In July 2019, 1,4-oxathiane, 1,4-dithiane and 1-oxa-4,5-dithiepane, 1,2,5-trithiepane, thiodiglycol , thiodiglycol sulfone and thiodiglycol sulfoxide as well as arsenic with up to 3.1 were found in the drainage wells mg / L and polycyclic aromatic hydrocarbons , which in their concentrations reached up to approx. 1.2 mg / L, can be determined.

Redevelopment

The district of Heidekreis has been working on the concept of risk assessment and the subsequent remediation of contaminated sites since mid-2014 . It is now certain that the pond will be opened at the end of 2019 in order to take solid and liquid samples from it. After the detailed investigations have been carried out, the district of Heidekreis will then use the new information to create a feasibility study in the next step. In 2019/2020 it is planned to secure the financial resources and to prepare and award the renovation. The security variant is to be implemented in 2021. A concept from the district of Heidekreis dated February 25, 2015 shows that, according to a rough estimate, 50 million euros are expected for the actual renovation work and an additional 2.7 million euros in other costs.

Lower Saxony's Environment Minister Olaf Lies declared in December 2019 that the pond “must and should be completely renovated”. He is certain that he will come to a viable solution with the federal government for the financing.

Web links

Commons : Dethlinger Teich  - Collection of images, videos and audio files

Individual evidence

  1. ↑ Small inquiry: Contaminated sites in the Dethlinger pond
  2. ^ Scientific services of the German Bundestag: Dethlinger Teich disposal of old armaments, Az. WD 7 - 3000 - 042/15 page 4 pdf
  3. ^ NDR report of October 30, 2019 on ammunition recovery
  4. ↑ NDR report from November 30, 2019 - 10,000 grenades in Dethlinger Teich
  5. ↑ Ongoing public information on the progress of the exploration work
  6. ↑ Press release of December 2, 2019 , accessed December 8, 2019

Coordinates: 52 ° 57 ′ 29.1 ″  N , 10 ° 8 ′ 32.3 ″  E