Emschergenossenschaft (Emscher Association) is building an underground sewerage tunnel from Dortmund to the mouth of the River Rhine for the renaturation of the Emscher River. In construction section 30, Wayss & Freytag Spezialtiefbau GmbH is building the required shafts as diaphragm walls or bored pile walls, partly with the support of a subcontractor. For this purpose, 70 diaphragm wall shafts with a total area of more than 82,000 m² are being built. Wall thicknesses range from 0.8 to 1.2 m. The shafts are up to 40 m deep.
Furthermore, numerous round and oval shafts, less deep and more restricted with regard to space available and height, are being carried out as overlapping bored pile walls. The diameters of the piles are 90 cm to 120 cm at a boring depth of up to 25 m. To relieve the stress on the groundwater horizon in the marl, extensive, deep holes were drilled with a diameter of d=0.9 m and depths of up to 50 m.