Technical specifications

Scope of work

Construction of a storage sewer tunnel

  • Length: 375 m
  • Internal diameter: 5.20 m
  • External diameter: 5.70 m
  • Min. radius: ∞ m
  • Min. cover: 5.50 m
  • Max. cover: 14.00 m

Segmental lining

  • Number of rings: 310 pieces
  • Ring split: 5 + 1
  • Segment width: 1.20 m
  • Segment thickness: 0.25 m

Construction method

  • TBM tunnelling using and EPB shield


  • Clay, clayey sands, Brussels sand


General data

Grootveldlaan Storage Sewer, Sint-Pieters-Woluwe, Belgium

Vivaqua, Brussels

Wayss & Freytag Ingenieurbau AG
in a joint venture

Construction period
2018 to 2020

Net construction costs
€ 14 million

Storage sewer tunnel
375 m
Construction Method
TBM tunnelling – EPB shield

More Information:

In Sint-Pieters-Woluwe, a municipality of the Brussels-Capital Region, located in the east of Brussels, a new storage sewer was built for the temporary intermediate storage of max. 8,000 m³ of rainwater. The construction of this storage was necessary because the existing sewer system of the municipality was overloaded during heavy rain events and flooding of streets and basements could occur.

The reservoir sewer was constructed by means of tunnel boring in segmental construction. An earth pressure shield was used for this purpose.

For the approach of the tunnel boring machine, a rectangular start shaft with overlapping bored piles was constructed at the "Koning Boudewijnplein" site. The shaft had a size of 17.40 m x 10.90 m, the bored piles had a diameter of 880 mm and reached a depth of approx. 17 m. The piles were cut in two.

From the starting shaft, the tunnel excavation ran almost parallel under the Grootveldlaan road for a length of approx. 375 m with a gradient of 1% before ending in a so-called blind hole. A target shaft for recovery of the tunnel boring machine was not provided. Therefore, it had to be dismantled through the tunnel, while the doubling, the cutting wheel and the shield tail remained in the ground. Transporting the shield, which is 4.85 m in diameter and weighs 55 t, through the tunnel, which is 5.2 m in diameter, presented a particular challenge.

A further difficulty arose due to the location of the construction site in an inner-city residential area with the associated problems, such as noise pollution for residents caused by construction machinery and delivery traffic, as well as the confined space conditions. The area of approx. 80 m x 25 m available for the site setup was not large enough to accommodate the complete TBM including all trailing units on the site for pre-assembly. In addition, it was not possible to lay out the launch shaft so large that the TBM could be completely set up for launch. For this reason, the trailing units had to be delivered successively, lifted individually into the shaft after the TBM had started up and integrated into the driving process. Also due to the lack of space, the backfill mortar had to be pumped through a concrete pipeline to the TBM, with a distance of almost 370 m to be covered at the end of the construction work.

Related Projects
Eppenberg Tunnel
Eppenberg Tunnel

Four-track extension of the Olten–Aarau railway line, Switzerland: the 2.6 km long Eppenberg tunnel helps to eliminate the traffic bottleneck.

Read more
Light Rail Line U81
Light Rail Line U81

Connection of the Düsseldorf main railway station with the airport, the Düsseldorf trade fair center and the Airport City business park, construction of an underground railway station at the airport terminal.

Read more
Liefkenshoek Rail Link
Liefkenshoek Rail Link

16.2 km long railway section connects both halves of the city of Antwerp on the banks of the River Schelde and creates a new railway line under the river for more than 100 trains per day.

Read more