The Italian Terzo Valico railway project has faced numerous challenges, and now it is confronted with the risk of explosions due to the discovery of gas pockets during excavation. Although not entirely unexpected in tunnel construction, the presence of a colorless and odorless combustible gas primarily composed of methane poses unpredictable dangers.
Deputy Minister of Transport Edoardo Rixi confirmed this new technical hurdle, which threatens to delay the project further. In response to a parliamentary inquiry, he stated, "Gas has been detected in the tunnels of the Terzo Valico of the Giovi, and we are carefully considering this in our evaluation of the project’s continuation. Seven of the twelve total work fronts are affected by gas, leading to a suspension of activities at these points while we work to remove the gas. Meanwhile, work continues on the other fronts."
The situation is particularly critical at the Val Lemme construction site in Voltaggio. Due to the gas leak there, Deputy Minister Rixi reported that "efforts are underway to enhance the air supply system to improve ventilation." The Val Lemme site, which connects the Radimero and Castagnola sections, is one of the most complex, with up to five simultaneous excavation fronts.
It remains unclear why this unexpected halt has occurred, especially since the Val Lemme site’s technical documentation, available on the official Terzo Valico website, anticipated the use of explosion-proof equipment and special procedures to manage the risk of explosions due to underground methane gas. Additionally, managing by-products from the excavation, including naturally occurring benzene, presents another challenge. Given these preparations, the sudden stop raises questions.
This issue at Val Lemme is just the latest challenge for the engineers of Cociv, the consortium responsible for the massive project under the Giovi. Another significant incident occurred at the Radimero site near Arquata Scrivia, where two tunnel boring machines (TBMs) were halted due to critical ground conditions—the first in June 2022 and the second in late October 2023.
These events add to a perfect storm of technical and geological difficulties, judicial investigations, site accidents, and contractor withdrawals, which have progressively delayed the project's completion. Initially expected to be finished by 2024, the timeline has now shifted to 2027. The project also relies on funding from the National Recovery and Resilience Plan (NRRP), with a theoretical deadline of 2026. There is still talk of opening the Terzo Valico in two phases, the first of which would involve partial operation on a single track.
Piermario Curti Sacchi
