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PORR constructs a green bridge for species protection in the northern Black Forest

The Enz Valley motorway crossing project got underway in October 2021. A roughly 4.8km stretch of the congested A8 between the Pforzheim-Nord and Pforzheim-Süd junctions will be widened to six lanes by the end of 2026. People, flora and fauna should all benefit from the new motorway, as the project involves an array of measures designed to promote nature and species conservation, in addition to new noise barriers. PORR Civil Engineering, Munich branch, secured the contract for Lot 5 with their plan for the construction of the new 64m-long Hagenschiess green bridge near Niefern. The earthworks began on 30 May 2022.

Visualisation of the Hagenschiess green bridge © Autobahn GmbH Niederlassung Südwest

The city of Pforzheim and the upper Enz Valley are located in the Central/North Black Forest Nature Park, which has an outstanding track record of protecting valuable habitats for many endangered animal and plant species. Nevertheless, the region is connected to the international transport network via the A8. The green bridge is being constructed to meet the needs of wild animals and ensure species protection. Most of the time, people drive under these green crossing aids without giving them a second glance, but they have two key tasks: to reduce the risk of collisions with wildlife and to join up habitats that are currently fragmented by highways and settlements. Deer, wild boar and lynx travel many kilometres a day, so they need a lot of space to move around. Small animals use these bridge structures, too.

Integral arch bridge to be built in two sections

The Hagenschieß green bridge is designed as an integral arch bridge on counterbearing foundations. Highly noise-absorbent motorway barriers shield the crossing animals from traffic noise and lights. As the six-lane expansion of the motorway is taking place alongside this project, the PORR team is required to to adapt to the traffic phases of the main Enz Valley crossing construction project. As a result, one half of the solid arch has been erected and is supported in the middle. Due to a lengthy construction break after the erection of the first half-arch, the green bridge is expected to be completed by autumn 2025.

Construction figures

  • Total length: 64m
  • Clear width between the abutments: 52.82m
  • Spacing of the counterbearing axes: 54.55m
  • Height at the critical point: 8.98m
  • Clear height at the apex: 12.36m

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