S-Bahn Line S21 Northern Connection, Berlin Central Station – Potsdamer Platz

Project Duration 2013–2026

Client
DB InfraGO AG

Location
Berlin, DE

As part of the expansion of Berlin’s S-Bahn network, a new double-track north–south axis is being constructed for the future S21 line. The project is divided into three construction phases (BA).

The scope of Construction Phase 2 (2. BA) of S21 Berlin begins at the structure currently being built for Construction Phase 1 (northern ring connection). Starting at Berlin Central Station (Hauptbahnhof), the planned alignment of Phase 2 runs southwards in two separate tunnel tubes through the government district towards Potsdamer Platz, where it connects underground—at the level of the Brandenburg Gate—to the existing structure of the North-South S-Bahn, the so-called “Heuboden”, a facility currently used as a stabling and reversing area that dates back to 1936. The S21 line then continues through the existing tunnel to Potsdamer Platz. Once Phase 2 is completed, S-Bahn lines running in the north–south direction will be able to operate either via Friedrichstraße Station or via the Central Station north of Potsdamer Platz. No stations are planned within Phase 2.

Construction Phase 2 of S21 runs largely through Berlin’s government district, located within the city districts of Tiergarten and Mitte (borough: Mitte). Along the alignment are numerous government buildings such as the Paul-Löbe-Haus and the Reichstag, as well as significant monuments including the Brandenburg Gate, the Memorial to the Sinti and Roma of Europe Murdered under National Socialism, and the historic landscape monument of the Großer Tiergarten. The route also lies in the immediate vicinity of Spreebogen Park and the River Spree.

Route Characteristics

The approximately 1.2-kilometre-long Phase 2 essentially consists of a section constructed by tunnel boring machine (TBM), as well as cut-and-cover tunnel structures in the northern and southern areas, including the demolition and reconstruction of the “Heuboden” section.

Northern Section

The northern part of the alignment is defined by the connection between the tunnel of Phase 1 and that of Phase 2 at Berlin Central Station. The completed Phase 1 route continues southwards in a cut-and-cover tunnel structure. This structure extends to the two TBM-driven tunnel tubes.

From a construction logistics perspective, the northern section is characterised by extensive site installation and intermediate storage areas, particularly for the two TBMs that start here. These facilities are located around Humboldthafen, Berlin Central Station, and Spreebogen Park.

TBM Tunnels

This section of Phase 2 includes the two single-track TBM-driven tunnels, approximately 865 m and 845 m in length, which run beneath the River Spree, Spreebogen Park, and Berlin’s government district, connecting the northern and southern sections. The lowest points of the tunnels lie approximately 22 m below ground level in the area of Spreebogen Park (measured to the tunnel roof). In addition to the two tunnel tubes, various preliminary and tunnel-supporting construction measures form part of this section.

Due to the significant distance between the tunnel tubes, each tube is equipped with an emergency exit and access structure.

Southern Section

The southern section—extending from the end of the TBM-driven tunnels to the connection with the existing North-South S-Bahn tunnel (“Heuboden”)—is characterised by newly constructed cut-and-cover tunnel structures and two additional emergency exit and access structures within the excavation pits. The northern of these structures connects the two tunnel tubes. At roughly the level of the Brandenburg Gate, the east and west tunnels converge and continue as a single tunnel structure up to the southern connection with the existing underground “Heuboden” tunnel.

From a construction logistics viewpoint, the southern section is dominated by extensive site installation areas in the vicinity of the Tiergarten, Platz des 18. März, and Ebertstraße. These areas are primarily used for the construction of the cut-and-cover tunnel structures and for the demolition and reconstruction of the “Heuboden” tunnel section, as well as for receiving the TBMs in their respective target shafts.

Scope of Services by OBERMEYER Infrastructure

OBERMEYER Infrastructure has been commissioned with HOAI service phases 2–4 and phases 5–6 for preliminary works (clearance drilling). The company is responsible for structural and civil works design, transport infrastructure design (including alignment), technical equipment (telecommunications, 50 Hz systems, traction power, signalling), structural engineering, expert assessments such as geotechnical reports, noise and vibration protection, environmental studies, surveying services, and the safety concept.

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