2,300 meters of solid rock rises above the 57 kilometers long Gotthard Base Tunnel, the world’s longest railroad tunnel, at its deepest point. The construction must not only withstand extreme mountain pressure but also substantial volumes of mountain water must be prevented from seeping in. To make sure the entire tunnel stays dry, two drains were laid in the floor of each of the single-track tubes. The drainage system separates the (clean) mountain water from the (mostly clean) "wastewater" that is drained off for removing impurities during operations or in the event of an accident. Every second, five liters of wastewater are carried away from each tunnel tube in every direction. The water is collected in catch basins at both ends of the tunnel and checked for any pollution.

A project of symbolic character

The measurement technology for the tunnel drainage originates from process automation specialist Endress+Hauser: 180 instruments, some of them explosion protected, and three measuring panels detect flow volumes and levels of mountain and wastewater, conductivity, the pH value and the turbidity of the wastewater. For Stefan Bürki, in charge of the project at Endress+Hauser Switzerland, the installation has a very special meaning: “I am proud to be part of this once-in-a-lifetime project!”
Find more information on Gotthard Base Tunnel here. Scheduled commercial services on the line are going to start in December 2016.