N5 Solothurn – Biel, Tunnel Birchi

The Birchi tunnel is a section of the N5 highway in the Canton of Solothurn (N5/2 section Nennigkofen – Zuchwil.

Main Data

  • Type of tunnel: double tube with 2 lanes per driving direction
  • Length: 2 x 1'400 m (2 x 700 m underground, 2 x 700 m open-cut)
  • Profile: horseshoe profile with bottom slab (in open-cut section base plate)
  • Excavation cross-section: 100 m²
  • Geology: lower fresh water molasse
  • Type of heading: pilot tunnel with partial excavation of roof section, face and invert, excavated with part-section machine
  • Stations: at both portals
  • Ventilation: longitudinal ventilation (jet ventilators)
  • Infrastructure: power supply, lighting, safety/ communication equipment, supply of water for fire fighting


Office for National Roads of the Canton of Solothurn


IUB Engineering Ltd. in consortium

Construction period


Construction costs

160 Mio. CHF

Scope of services

  • Construction project
  • Tender and comparison of tenders
  • Execution project
  • Supervision of works
  • Documentation on the project

According to the terms of reference of the overall project management, the consortium - under the leadership of IUB (certified according to ISO 9001) - drew up a QC plan with annual audits for all partners (project work and supervision of works).