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Elaborate drilling process: Workers lay sewage pipes for expansion of S13 in Beuel

Elaborate drilling process : Workers lay sewage pipes for expansion of S13 in Beuel

In an elaborate drilling procedure, the city's civil engineering department is having a sewer relocated in Platanenweg. The work is part of the extension for the S13 light rail line.

The next major section in the S-13 project is almost complete: For the extension of the light rail line, the sewer in Platanenweg will be renewed and relocated by this Wednesday. The new pipeline is also to run underneath the rail line and has already been laid in part during nighttime operations. There had been a night construction site for example also in November in Vilich. The city's civil engineering department has budgeted 3.34 million Euro for the work. The current flooding of the Rhine has not affected the work due to the relative proximity to the construction site, says head of the civil engineering office Peter Esch.

A canal in Gerhardstraße in Vilich was already reconstructed in a similar way in 2017. This time, the work is taking place in the area of Platanenweg 27, the civil engineering office informs. In the future, the sewer there will run below the intersection of Siebenmorgenweg and Auguststraße, cross under the railroad tracks and Königswinterer Straße, and lead into the local drainage system below the Bröltalbahnweg.

Sewer construction under the DB tracks

Because the sewer pipes cannot be inserted underneath the railroad tracks by digging a trench, the civil engineering company commissioned is working using the so-called pipe jacking method: A twelve-ton tunnel boring machine excavates the soil and transports the debris into a large construction shaft. A cable excavator lifts the sewer pipes one by one into the shaft so that the machine can grout them in the next step in the tunnel. Typically, the pipe jacking method is used when tunneling under traffic routes or for pipeline construction.

For the sewer construction in Platanenweg, the reinforced concrete pipes are assembled underground to form a 60-meter-long reservoir with a diameter of almost two meters. "This is real precision work," says Ralf Waßmann, the city's senior construction manager. He added that a special camera had been attached to the head of the tunnel boring machine to follow the boring. "The recordings are transmitted directly to a central switching station at the construction site," says Waßmann. From there, a computer system controls the drilling, and (re)adjustments have to be made every now and then. "The machine always has to maintain a certain inclination," Waßmann explains.

The pressure is also adjusted now and then, as different layers of earth have to be drilled through. Eight meters below the earth's surface, the new sewer is being laid - normally a depth of 1.5 meters is sufficient for sewers. However, due to the heavy load caused by the traffic on the railroad line, the pipeline has to be set deeper. The pipe jacking method is considered to be particularly gentle on the soil, as it hardly damages the earth infrastructure. However, the construction efficiency of the method is offset by a high price: The 3.34 million euros mentioned for the sewer project in Platanenweg are exceedingly expensive, says Esch.

Ballast, gravel and sand bear witness to history

The civil engineering company Sonntag, which specialises in pipe jacking, put the tunnel boring machine into operation last Friday. At noon, it produced the first tons of construction debris in a trough from the tunnel. The crumbled rock debris consists of crushed stone, gravel and sand - and tells a piece of history: "You can tell from this rock that an old branch of the Rhine runs through here," says Esch. Due to the proximity to the body of water, the drilling process is not entirely without danger, as there is also a risk of flooding in this area. Flooding due to the rising groundwater level could affect the work. Another risk that could jeopardise the construction work is explosive ordnance that still lies underground, the civil engineering manager said. "During World War II, an ammunition transporter was hit by a bomb not far from here, and the charge spread through the area." Before any civil engineering projects, therefore, the Explosive Ordnance Disposal Service would always have to probe the affected construction areas with special detectors, he said. If munitions are found, the clearance service would have to recover them first. In the course of the S-13 construction project, however, this (case) has not yet been experienced, says Esch.

Drilling at night

Strict conditions for the construction project were imposed not only by the authorities but also by Deutsche Bahn: For the work directly underneath the railroad line, work was to be carried out in 24-hour operation on Monday and Tuesday, says Esch. Corresponding work cycles had therefore been planned for the period of crossing under the track. Although the underground drilling and pressing in of the sewer pipes would be largely noiseless, this would not apply to a power generator that had to be operated continuously during the work. Waßmann said before the work began that the aim was to keep noise pollution from the generator to a minimum, but that he could not rule out disturbing the peace at night. The city had therefore offered residents to stay overnight in a hotel during this time.

This Wednesday, the work is to be completed. After that, the gap between the pipe and the soil will be grouted again. The city expects the civil engineering work on Platanenweg to be completed on February 6.

MORE TRAINS - Extension of the S13

In order to better connect Beuel to Cologne and Cologne/Bonn Airport via the S-Bahn, the S13 line is being extended. So far, the light rail line only runs from Horrem via Cologne and the airport to Troisdorf. Because of the dense freight traffic, additional tracks will have to be laid on the line between Troisdorf and Oberkassel. The project also includes the construction and renewal of numerous bridges, noise barriers, and underpasses and flyovers in this area. Two additional stops are planned between Troisdorf and Oberkassel: Bonn-Vilich and Ramersdorf. The current work in Platanenweg is connected with the construction of a wider rail line.

Original text: Abir Kassis

Translation: Mareike Graepel