The construction of the second Gotthard Tunnel has hit a major hurdle with the discovery of arsenic in the rock.

The Federal Roads Office (Astra) was surprised by the find, as geological reports had not predicted it.

Initially, 3,000 tons of arsenic-laden material were dumped into Lake Uri as part of a restoration project, but further dumping was halted after the contamination was identified.

A risk analysis revealed that up to 400,000 tons of the excavated material could be arsenic-contaminated.

Plans to use the material for lake restoration have been abandoned, and it will now be repurposed for a park project in Airolo, with approval from local authorities.

Environmental concerns remain high as officials work to mitigate potential damage.