Sealed former potash shaft site of the Gewerkschaft Lohra in Obergebra, where the underground workings served as a Heeresmunitionsanstalt from 1935 and munitions were cleared after 1945.
The Gewerkschaft Lohra was a potash enterprise established in 1911 at Obergebra in the Grafschaft Hohenstein by detaching a portion of the concession of the neighbouring Gewerkschaft Gebra. The single shaft, Schacht Lohra, was sunk from early 1912; final water seal was achieved at 193 metres on 18 January 1912 and sinking was completed at 720 metres on 6 September 1912, having intersected a 15-metre potash seam at 685 metres depth. The two-shaft regulatory requirement was met by an underground breakthrough to the adjacent Schacht Gebra.
The concession area lay within the Wintershall-Konzern sphere of influence. Potash production ran from 1912 until 1933 when the workings, together with those of the Gewerkschaft Gebra, were handed over to the Wehrmacht for use as the Heeresmunitionsanstalt Obergebra. From late 1935 munitions were stored underground and assembly work was later carried out.
After the end of the war, from spring 1946, munitions clearance and chemical warfare agent recovery took place at the Schacht Lohra area. The site at Obergebra is now part of the Stadt Bleicherode and the former works area has been made available as a commercial and industrial zone.
The Gewerkschaft Lohra was founded in 1911 by the detachment of a portion of the concession area of the Gewerkschaft Gebra, which had itself been established on 1 August 1910 through the purchase of field rights from the Kaliwerke Aschersleben and from Hermann Schmidtmann. The Lohra field lay within five Prussian maximum-size fields in the Gemarkungen Rehungen, Sollstedt, Wülfingerode, Friedrichsroda, and Lohra, and it bordered in the north on both the Kaliwerke Sollstedt and the Prussian fiscal Kaliwerk Bleicherode, the latter boundary extending for approximately 6 kilometres. The Wintershall-Konzern held a controlling interest in both the Gebra and Lohra concerns.
Sinking of Schacht Lohra began after the site east of the Schacht Gebra was established. The final water seal in the shaft tube was achieved on 18 January 1912 at 193 metres depth, after which sinking proceeded rapidly. Younger rock salt was intersected at 540.50 metres on 7 June 1912. The potash horizon was reached at 685 metres on 21 August 1912, revealing a seam 15 metres thick of which 4.5 metres was hard salt (Hartsalz) and 10.5 metres carnallite. Sinking was halted at 720 metres on 6 September 1912. Timber lining was completed by early November. Ore-loading drives (Füllörter) were set north and south at 701 metres depth.
The two-shaft regulatory requirement, which obliged each mine to maintain a second accessible exit, was satisfied through an underground breakthrough with the adjacent Schacht Gebra. The surface buildings of the Schacht Lohra complex included a headframe with shaft hall, a winding machine house, a boiler house, a water supply installation with bored well and elevated tank, an office and pithead baths building, workshops, a magazine, and a gatekeeper's lodge. A Drahtseilbahn connected the shaft to the Kaliwerk Sollstedt, where the raw salt from both the Gebra and Lohra shafts was ground and processed. In 1919 combined sales from both the Gebra and Lohra concerns amounted to 1,140,540 Doppelzentner of hard salt and 38,095 Doppelzentner of 20-per-cent potassium fertiliser.
Potash production from the Schacht Lohra and Schacht Gebra ceased in 1933. In 1935 the Wintershall AG handed over the underground workings, by then consolidated as the Kalibergwerk Gebra-Lohra, to the Wehrmacht for conversion into the Heeresmunitionsanstalt Obergebra. By late 1935 the first munitions arrived in the underground storage chambers. From 1940, assembly work on munitions was also carried out underground in two new underground munitions workrooms. The facility also served from 1940 as a dismantling point (Zerlegestelle) for captured munitions and blindgänger returned from the front. Near the entrance of Schacht Lohra, explosive ordnance was decommissioned in open air (delaboriert).
At the end of the war, US forces entered the Obergebra area. On their withdrawal in favour of Soviet forces, German workers began clearing munitions from the shafts from spring 1946. The Firma Rabebau from Bleicherode was contracted in April 1946 to carry out the munitions clearance. Simultaneously, chemical warfare agents stored underground — including Chloracetophenon — were recovered; the wooden protective casings of damaged barrels were burned near the Schacht Lohra entrance, generating severe pollution of the site. The Soviet military command's Produktionsbefehl Nr. 9 required the rapid resumption of potash production. In March 1946 rehabilitation work was extended to Schacht Gebra as well, to provide the mandatory second exit. The workforce re-entered the underground workings after the munitions clearance was completed.
The Kaliwerk Sollstedt subsequently incorporated the Schacht Gebra workings as a training facility (Ausbildungsstätte) after the Second World War. The Schacht Lohra site lies in Obergebra, which became a part of Bleicherode in 2007 and then a district of the Landgemeinde Stadt Bleicherode from 1 January 2019. The former works site is now available as a commercial zone (Gewerbegebiet).