The small village of Sissach, near Basel, in Switzerland is one of the nicest Swiss villages in the country, but the serenity is plagued each rush hour by heavy commuter traffic. The solution was a bypass tunnel running through the Chienberg hill to the north side of the village. Shallow cover, unconsolidated material at the portals, a TBM pilot tunnel, and the potential for squeezing ground conditions distinguish the Sissach tunnel from many tunnels currently under construction in Switzerland.
The 2284 m (7500 ft) long Sissach bypass tunnel runs a maximum of 120 m (395 ft) beneath the Chienberg hill and beneath the picturesque homes of the Sissach village. It was originally intended to run the two-lane bidirectional bypass up and over the hill on the surface, but protests by the local villages forced the local Canton government to adopt an underground route for the heavy commuter traffic currently passing through the village.
To accommodate the shallow underground route, the alignment is divided into three separate sections: a section of 550 m (1800 ft) cut-and-cover and 200 m (656 ft) cover and cut on the west end, followed by a 1440 m (4725 ft) length of mined tunnel, and a 94 m (308 ft) section of cut-and-cover at the east end.
The first 550 m (1800 ft) of cut-and-cover on the west end of the project was completed under a separate contract and included the boxed section over the Ergolz River. The contract for the main bypass civil works, including the mined tunnel, was awarded to the Arge Chienbergtunnel Sissach, a joint venture led by the Batigroup, Switzerland™s