The tunnel vault is lined with a watertight sealing film that forms a kind of umbrella over the tunnel. The water from the mountain is thus channelled into the lower area of the tunnel, where it is collected in drainage pipes. Including the water from the existing tunnel pipes, up to 160 l/s of water is collected at the southern portal, with around 50 l/s being collected at the northern portal. Due to the temperatures inside the mountain, the water discharged at the tunnel portal has a temperature of between 15 °C and 20 °C depending on the time of the year.