Final double breakthrough at Emscher sewer 17 Aug 2017

After 25 years of excavation on the 51km Emscher deep gravity sewer project in Germany, the double breakthrough on the two 10km long main collector tunnels has completed the work. The two 3,397mm EPB shields from Herrenknecht broke through into the target pit at Oberhausen-Biefang on June 12, 2017.

Peak performances of up to 177m per week and 582m per month were achieved between October 2014 and June 2017 for construction company Porr, and support from Herrenknecht kept machine availability above 95% for the entire period. These were the only machines in the entire project to use segmental lining, and with an inside diameter of 2.6m the twin tubes are among the smallest segmentally lined tunnels in the world.

The Emscher river will be cleaned and returned to nature

The entire tunnelling system, with a length of around 85km, was designed to be compact. This resulted in challenges during construction including several partially tight curve radii of up to 200m; excavation below the A2 motorway and close to inner city supply lines; and a drive through a 300m long geological fault zone with sandy and groundwater-bearing subsoil and Emscher marl.

Since 1992 more than 400km of new underground sewer tunnels have been constructed on this project. These also faced many challenges along the way including diverse ground, depths of up to 40m, and long pipe jacking distances. Herrenknecht has provided bespoke technology throughout including small diameter AVN pipe jacking machines, EPB shields using pipe jacking and segmental lining, and a vertical shaft sinking machine to sink a 23m deep launch shaft.

Over 60km was supported by navigation, communication, data management and safety systems from partners VMT. Herrenknecht Formwork produced segment moulds and MSD supplied rolling stock, a lifting beam and a tilting table for the pipe plant in Gelsenkirchen.

Pipe jacking and segmental lining methods used

The Emscher river, whose source rises in Holzwickede to the east of Dortmund, passes through a series of cities in the German Ruhr area on its 80km path before it flows into the Rhine. Since the beginning of industrialization around 1850, the small lowland river was used as an open channel for sewage, flood and rainwater and degenerated into the dirtiest river in Europe.

With the renaturation of the stream, sewage and rainwater will be separated, drained away underground and purified in intermediate treatment plants. As a result the river will become clean again and improve the quality of life for people living in the Ruhr area. Commissioning of the Emscher sewer is planned for the end of 2020.