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June 10, 2015
A tunnel project in the Ruhr region of Germany is helping to restore a natural river system that has long been used for wastewater.
On a cold and sunny day in the German city of Gelsenkirchen, two priests, one Catholic and one Protestant, said a couple of prayers over a bronze statue of Saint Barbara. The Catholic priest sprinkled some holy water, and the saint was lowered into a little shrine hung inside a shaft. A tunnel would be dug here under the Rhine-Herne canal. The blessing was followed by the “launch” of a tunnelling machine with a bottle of champagne.
“It’s a tradition to call for a blessing on a tunnelling project,” explains Günter Osthoff, Head of the engineering company Wayss & Freytag, which owns the machine. Barbara is the patron saint of both tunnelling and mining, and the project to build a 70-kilometer underground wastewater canal parallel to the Emscher River brings the two industries together.
The area, part of the Ruhr region, was a major source of coal in the last two centuries, and the landscape is still marked by its past. The mines caused major subsidence of up to 20 meters, and 30% of the region is now below the groundwater level.
The Emscher River and its tributaries were used as a sewer. Running between concrete banks, they carried the wastewater for 2.5 million people and the region’s industry.
“ That had the advantage that one could keep track of problems resulting from subsidence,” notes Osthoff. Now that the mining has almost ended, the whole river system – all 300 kilometers – is being restored to its natural state. ”
The ambitious project was initiated by the Emscher Cooperative, which was set up in 1899 and is the oldest wastewater disposal coordinating authority in Germany. A century ago, the Cooperative turned the rivers into sewers, and now it is transforming them back into places of recreation and enjoyment.
At the same time, the wastewater has to go somewhere, and that’s where the tunnel builders come in. The ceremony on 1 February was the fifth that Osthoff, who heads up the Wayss & Freytag Emscher project, has attended. The company now has a total of five tunneling machines operating simultaneously, and another two are likely to be added.
“We are responsible for 47 kilometers of the main tunnel from just outside Dortmund to Bottrop,” says Osthoff. “The tunnel starts with an inner diameter of 1 600 millimeters and finishes with 2 800 millimeters, and each section has to have its own machine.” The machine in Gelsenkirchen is the largest: It has to drill a 3 700-millimeter hole to leave room for the tunnel lining pipes.
As the machine drives through the earth, the pipes are rammed in behind it. “It’s not like a railroad tunnel through a mountain, where two tunneling machines start at either end and meet in the middle,” explains Osthoff. “This tunnel is divided into more than 100 sections, and each one has a shaft at the beginning and another at the end.”
The friction between the earth and the lining pipes would be too great if the pipes had to be forced in too far, so the shafts cannot be too far apart. The section under the Rhine-Herne canal is 350 meters long, and the longest is about 1 000 meters.
Each shaft is surrounded by a little island of industrial activity as the earth is dug out, raised to the surface and disposed of. A battery of generators supplies electricity.
“Mains electricity would not be flexible enough,” says Osthoff. “Sometimes our shafts are in urban areas; sometimes they are in very rural areas. We needed a power supply which was flexible and independent.”
Atlas Copco has so far supplied 22 portable generators, of which four or five are linked in series at each of the five shafts which are operating at any one time. They’re equipped with a control module which ensures that each of the generators works only when needed.
“There are very different loads, depending on whether the tunneling machines have to work at full power or if they are going through relatively soft material,” says Osthoff. By turning the generators off, the software saves energy and wear-and-tear.
The Emscher project has the widespread support of area residents, who are prepared to put up with the inconvenience of construction work until 2017. “The people here are used to industry,” says Osthoff, “and everyone can see that this project makes sense.”
“ Everyone can see that this project makes sense. ”
Written by Michael Lawton