In Gelsenkirchen, the consortium "Holzbach 2", consisting of the companies Eiffage Infra-Nordwest GmbH, Eiffage Infra-Vortriebstechnik GmbH (now Eiffage Infra-Spezialtiefbau GmbH) and Smet Tunnelling N.V., was assigned to construct the Holzbach sewer. Over a length of 5.9 km, the construction is carried out with pipe dimensions of DN 2200 to DN 2800 at depths of 10 to 13 m below ground level. The constructuion task includes the associated rainwater treatment facilities. Within the scope of the renaturation of the "Holzbach" stream, the dirty water will be separated from the clean water and discharged into the new sewer.

In addition to the pipe jacking work, the construction project includes extensive special civil engineering work for the construction of launch, target and drive-through excavation pits. Mainly bored pile walls, CSM walls (cutter-soil-mix) and sheet pile walls are used. 12 shaft structures are produced in in-situ concrete construction at depths of up to 15 m.

The construction project is located in the urban area of Gelsenkirchen and Herten and runs mainly parallel to the Holzbach. The river Holzbach flows into the Emscher.

The construction section Holzbach 2 is a component of the overall measure comprising a total of 3 construction sections and follows on from section 1, which is also being carried out by the consortium.