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Schönheide Sewage Diversion Tunnel

The Eibenstock drinking water reservoir was built in the Erzgebirge between 1974 and 1983. To avoid sewage contaminating the reservoir, a sewage diversion system was created, which ensured that the waste from the communities around the reservoir was transferred to a clarification plant near the lower course of the reservoir. It was imperative to renew the system on account of increasing amounts of sewage and technical requirements. The responsible joint venture proposed that the new diversion tunnel should be headed by means of a TBM rather than by drill+blast. The ground mainly consists of "Eibenstöcker tourmaline granite", which exists in a large number of forms. Apart from fine and coarse grained granites, there are weathered and eroded sections with in some cases highly kaolinised granite. Veins of quartz, tin and iron ore as well as clayey faults, revealing plastic properties when exposed to water were explored or were already known. In some parts of the tunnel route, tin and iron ore mining had formerly been carried out with varying intensity. However, the tunnels and working chambers were only partly charted. No maps existed for really old mines - as a result, it was not possible to identify the position of some mines in relation to the tunnel that had to be driven. The heading concept thus had to take into consideration that possibly old mines filled up with water might be encountered, resulting in sudden water inflows laden with debris. As a result, pre-investigations were carried out using 64.5 mm diameter bores over a length of 35 m in zones where it was feared old workings might be present as well as lateral pre-bores in the wall area down to a depth of 10 m.


  • Country: Germany
  • Region: Sachsen
  • Tunnel utilization: Utilities
  • Type of utilization: Sewage
  • Client: Zweckverband Wasserwerke Westerzgebirge
  • Consulting Engineer: Plawac, Taberg-Planungsbüro Ost, Ingenieurbüro Preussner
  • Contractor: Philipp Holzmann AG, Ed. Ast u. Co.
  • Main construction method: Trenchless
  • Type of excavation: Tunnel boring machine (TBM)
  • No. of tubes: 1
  • Tunnel total length: 4,965 m
  • Cross-section: 3.50 m diameter, 9.6 m² cross-section
  • Contract Volume: 18.5 mill. DM
  • Construction start/end: December 1997 till December 1999
  • Opening: 2nd quarter 2000