Prior to its construction, all traffic had to use the historic high-level route via the 1.8 km (1.1 mi) long Furka Summit Tunnel, which was only available seasonally due to the threat posed by heavy snowfalls.

An innovative permanent support system was used, comprising rock anchors and a shotcrete coating, which included the first use of polyurethane-based grouting within a railway tunnel.

These seasonal cycles of closures and reopenings required civil engineering works each time, as large sections of the railway's overhead electrical lines had to be dismantled and reinstated as well.

[citation needed] However, these estimates proved to be drastically inadequate as the project proceeded, with figures in excess of 300 million francs being reached prior to the base tunnel's completion.

One such technique involved the application of a recently developed polyurethane-based grouting to make the rock surrounding the tunnel portals impermeable.

Areas of particularly high rock pressure were addressed via the excavation of an elliptical or circular profile and the application of steel ribs.

Engineers were guided in the use of support measures by a series of geological studies, along with construction experience, to predict and monitor systematic deformation.

Typically 400 metres of the tunnel were lined each month, this rate being supported via five individual shotcrete machines that were operated simultaneously.

This programme, costed at CHF 190 million, largely revolves around the refurbishment of the tunnel's structure, the wholesale replacement of the track and trackbed, as well as the incorporation of various safety measures.