The pontoon was design with a hydraulic propulsion system driving wheels against the tunnel side walls. A full hydraulic excavation arm was also included.
A VVR oil reservoir was used to minimise environmental impact in case of spillage, and to reduce system size and weight.
The complete hydraulic system and pontoon had to be modular so it could be lowered down via an access hole to the tunnel, then assembled underground.
Watch a video of the pontoon excavator in trials below.