Trento Proposes New 1.2 km Tunnel to Repair Landslide-Damaged Gardesana

Seventy-five billion lira in expenditure and, if everything goes as planned, 18 months of construction. Here is how much it will cost, in terms of money and inconvenience, to create the new connection tunnel between Riva and Limone, following yet another devastating blow to the future of that section of Gardesana Occidentale from last Friday’s landslide.

To illustrate what has now become the direction of the Provincia di Trento, yesterday, in the regional palace, there were the public works assessor, Sergio Casagranda, the head of Civil Protection, Engineer Claudio Bortolotti, and the director of the road works service, Engineer Raffaele Da Col.

The tunnel solution and its features

A tunnel that, given the construction timeline, will inevitably raise doubts, but which appears as an essential choice. “Back in 1999,” explained Casagranda, “Engineer Eugenio Castelli, whom we commissioned to prepare an analysis of the area’s hazards and to assess intervention priorities, provided a very worrying overview, describing that section of Gardesana as ‘indefensible’.”

Therefore, at that time, a preliminary project was drafted to build a tunnel that would definitively resolve the issue. The landslide last week, which caused greater damage than the February 1999 event from a traffic perspective—dragging a section of the roadway into the lake—convinced us that the only feasible solution is the tunnel.”

The tunnel will enter Rocchetta near the intersection with the Ponale road and exit near the Sperone valley, which will be one kilometer and two hundred meters long, seven meters and a half wide, six meters and eighty centimeters high, and is expected (conditional tense) to be completed by May 2002. From inside the gallery, another smaller tunnel will branch off (two and a half meters wide and two meters and seventy centimeters high), connecting with the old Gardesana and serving for quick interventions in emergency situations.

“It’s a new technique,” stated Bortolotti, “which allows us to avoid building two parallel tunnels and which we have already implemented in Verla and Faver.” What about the future of Gardesana? The remains of State Road 45bis will be repaired (the cost expected is in the order of a few hundred million), but it will no longer be used for civilian traffic. It will host part of the construction site for the company building the new tunnel and will subsequently be used by emergency vehicles in case of need.

As for the timeline, it will be “short”: the provincial government will need to approve the project and secure the necessary funds. Five or six months will be needed for the preparation of the executive project and for allocating the funds, followed by the European tender process, and finally, in December 2001 or January 2002, the works will commence.

Meanwhile, until summer 2002, only boats will connect Riva and Limone. Bortolotti remarked, “I do not take on such overwhelming responsibilities.”

The safety debate and alternative projects

Indefensible. No other words are needed to explain that, on Gardesana, any engineering work would be ineffective in the event of new (and quite probable) landslides. Ineffective tunnels and cement retaining walls—“the hazardous fragments are so enormous that these structures would risk being crushed,” explained Casagranda—and the solution proposed days ago by Riva’s deputy mayor, Pietro Mattoetti, to use a Bailey bridge over the damaged stretch of the highway caused by the massive rocks fallen last Friday, are both utterly unviable.

Therefore, a tunnel, plain and simple. And what about the residents of Limone? “The tunnel will mainly serve them,” explained Claudio Bortolotti, “as many go to Riva throughout the year for studying or work.” The inconveniences of the upcoming months are a necessary evil.

“Yes,” continued the head of Civil Protection for Trentino, “I cannot assume criminal responsibility, but above all, moral responsibility, for putting these people’s lives at risk. In this context,” Bortolotti concluded, “it would be appropriate that, alongside our works, similar interventions are carried out on the Lombard stretch of Gardesana.”