Wayss & Freytag, Züblin win dewatering tunnel contract at German mine

12 October 2021

A 50-50 consortium comprising Wayss & Freytag and Züblin has been awarded a contract from RAG Aktiengesellschaft to build a new mine water drainage tunnel for the former Ibbenbüren mine in Germany.

The multi-million Euro contract involves more than 7km of tunnel to drain the mine – which closed in 2018 – where water has been rising ‘in a controlled manner’ since the deep dewatering system was shut down.

Excavating the 3.6m ID segmentally-lined tunnel – which will include an invert channel for draining off mine water – will be achieved using two tunnel boring machines working from separate access points. A 250m-long section will be excavated as a launch pit, and a 70m-deep central shaft with a colossal 32m internal diameter will also be sunk.

In addition, an existing mine shaft which is partially filled below the connection of the new tunnel, is to be reinforced to allow the new drainage tunnel to be connected to it at a depth of 100m, through which the mine water will be conveyed to the Gravenhorst treatment plant.

Construction work is expected to begin in November 2021 and be completed by end of 2024.