Hanover

B3 Südschnellweg

Working in a consortium to rehabilitate the B3 Südschnellweg

Road tunnel instead of bridge

The Südschnellweg, with two lanes in each direction, was built in 1954 and has since been the only efficient and flood-free east-west connection in the south of Hanover.

As part of the renovation, the existing bridge over Hildesheimer Straße and Schützenallee in the Döhren district will be replaced by an underpass. To this end, the consortium will first construct a 940 m long temporary bridge parallel to the elevated road and then demolish the existing bridge. Subsequently, a 1,100 m long road tunnel with ramp structures will be built to pass under Hildesheimer Straße and Schützenallee.

Preparations and special civil engineering for temporary bridge

In 2023, the first measures for the special civil engineering work began, including the construction of a 1,100 m long diaphragm wall on the north side of the Südschnellweg as the foundation for the temporary bridge and part of the future tunnel. This work was completed on schedule and to the required quality standards at the beginning of 2024, allowing the special civil engineering work to be handed over to the structural engineering team. Work also began on the catch dams, which will later form the approaches to the temporary structure.

Self-sufficient, energy-efficient construction site

In order to reduce the ecological footprint of the construction site, a site-specific wastewater treatment plant was also built. This enables self-sufficient treatment of construction site wastewater, eliminating the need for transport routes for wastewater disposal and thus saving CO₂ emissions. In addition, the installation of a photovoltaic system on the container roofs is currently being examined in order to supply the construction site with green electricity. The goal: to put sustainability at the top of the project agenda.

Challenging steel construction for temporary bridge on a tight schedule

With the completion of the diaphragm wall work, the civil engineering team began installing the steel structure for the 938-meter-long temporary bridge, which was built parallel to the existing bridge. The structure consists of 18 individually load-bearing sub-structures and was precisely assembled using synchronized heavy-duty cranes. More than 40 bridge piers were constructed for this purpose; the steel components came from two suppliers producing in parallel. A highlight was the assembly at the Hildesheimer Straße/Willmerstraße intersection during tightly scheduled weekend closures.

Smooth coordination through Building Information Modeling (BIM)

"For Hanover and for us as a consortium, this is a project of special dimensions that requires meticulous coordination of the trades involved: special civil engineering, earthworks, pipeline and sewer construction, road construction, track construction, civil engineering, and steel construction. Without BIM modeling, the timely completion and permanent cost control of such a complex project would be inconceivable," explains PORR project manager Konstantin Jury. Occupational safety and environmental protection are also integrated into the processes. All construction materials are recycled to the highest possible standard, amphibians and other animals are kept away from danger zones by protective fences, and damage-free flood drainage is also ensured.

Temporary bridge opened to traffic

At the end of October 2024, the temporary bridge was officially opened to traffic. This commissioning created the necessary construction space to gradually dismantle the old Südschnellweg bridge and then start tunnel construction.

Demolition of the dilapidated existing bridge

In an impressive team effort, the ARGE PORR, PORR Spezialtiefbau and Hagedorn consortium reached a decisive milestone on the Südschnellweg in June 2025: the complete demolition of the dilapidated bridge over Hildesheimer Straße was completed on schedule. As demolition by explosion would have been too risky due to the proximity of buildings and infrastructure, the team opted for a precisely planned, section-by-section demolition process using heavy equipment. Six demolition excavators with concrete shears and hydraulic chisels worked their way through the structure synchronously from both sides. The demolition of the middle section of the bridge, the so-called hollow box, was particularly challenging. Massive hydraulic chisels were used here to create access points through which concrete shears then cut the bridge in half. The removed material, around 15,000 tons of concrete and steel, was roughly crushed on site. After separation, it will be reused as a construction road, fill material, or aggregate.

Second phase of diaphragm wall work

After the successful demolition, the second diaphragm wall phase began on the south side of the Südschnellweg in spring 2025. There, another 1,100 m long, up to 30 m deep diaphragm wall is being constructed to prepare for tunnel construction. Only after completion can the excavation between the parallel diaphragm walls begin.

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