Byggarbetare med fraktionsrapport i surfplatta

Case study

Karlastaden in Gothenburg

How can 1,400 m³ of clay be got rid of in the middle of Gothenburg?

Sugbilar vid borrhål

With the new Karlastaden being built on Hisingen in Gothenburg, the district needed to get its water supply from the mainland on the other side of the river. This means that a new 1.3 km water pipeline had to be laid using directional drilling, under the Göta River, starting in a heavily trafficked area in central Gothenburg. Sortera’s task was to use suction trucks to remove the large amounts of clay that were pushed out of the borehole. 

Controlled drilling under the Göta River 

Controlled drilling involves drilling a channel underground, using GPS guidance and a drill bit that can be controlled both laterally and vertically. In this case, the drilling would start at a location near Järntorget in central Gothenburg and end at Lindholmen on the other side of the Göta River. Drilled material is gradually pushed backwards and out of the borehole. 

Drilling without interruption, six days in a row 

In central Gothenburg and around the river, the soil mostly consists of bentonite and clay. Therefore, the drilling had to be done without interruption to avoid the risk of the pipeline getting stuck underground. The contractor BAB Rörtryckning is one of Sweden’s leading companies in directional drilling, but even for them this was a special project with very little room for error. 

BAB needed a partner who could continuously transport away the mud mixture that would be pushed up into the borehole during the six days that the drilling would take place. We at Sortera are of course proud that BAB chose us for this demanding project. 

Suction trucks in shuttle service across Älvsborgsbron 

Every minute of drilling pushed 1–2 m3 of material out of the borehole at Järntorget, a total of approximately 1,400 m3. These are very large volumes in a short time, but something that Sortera’s facility at Hisingen could handle, even if it would require adaptations and around-the-clock work. 

The major challenge instead lay in creating a logistics system where suction trucks could suck up the mud mixture around the clock and then shuttle over the Älvsborgsbron bridge to unload it at the facility. 

“We had to plan for continuous service, despite rush hour traffic and the risk of traffic disruptions in the city. We also needed to take into account the traffic at the Torslanda factory around shift changes when 5,000 people are going to and from work. This was simply a very large-scale project, in high-traffic areas, with a small window for disruptions – and BAB needed our services around the clock,” explains Danny Jay Höglund, Sortera’s Project Manager for Special Services. 

A credible overall solution: five suction trucks and 24/7 availability 

The solution Sortera presented meant that five suction trucks would operate continuously throughout the drilling period. To avoid driving in rush hour traffic, trailers were also loaded. The trailers would function as a safety buffer in the event of unforeseen traffic disruptions. 

The fact that Sortera was able to present a solution where the excavated material was handled in-house on a 24/7 basis, relatively close to the drilling site, further increased the credibility of the solution and contributed to Sortera being awarded the contract. 

The result: trouble-free drilling and the water pipeline is in place 

How did it go? Well, the project went exactly according to plan. The water pipeline, with a diameter of 900 mm, is now in place 12 meters below the Göta River. Several Sortera teams collaborated on this project to provide the customer with the service that was required. Thanks to good planning and good risk management, the people of Gothenburg did not see Första Långgatan flooded by mud slurry. 

Tommie Mörkvist at BAB Rörtryckning is satisfied: 

“A very good collaboration! Sortera’s staff are 100 percent service-minded, and have really good equipment at their disposal. They found a solution to all the tasks they were faced with. Right from the start, we perceived them as trustworthy and solution-oriented, and they have truly lived up to our expectations!” 

Key to success: Capacity and flexibility 

In this project, the key to success was a combination of capacity and flexibility that could only be achieved thanks to smart solutions and Sortera being able to offer a comprehensive service in-house.