From west to east, the Uetliberg Tunnel undercuts two parallel hills, Ettenberg and Uetliberg.

The molasse sections (upper fresh water molasse) consist of alternating flat-bedded strata of hard sandstone and soft marl. The maximum overburden of the tunnels under the Uetliberg is approx. 320 m.

The Eichholz and Uetliberg molasse sections are reached by excavation through the three soft ground sections of Gjuch, Diebis and Juchegg.

The soft ground sections consist mainly of heterogeneous moraine, partly overlaid with loam.

All the soft ground sections are entirely on partly under the groundwater level.