Precision drilling in Switzerland: S-curve under busy streets

For the installation of this water main, a horizontal directional drill was designed to minimize disruption in the urban environment. This drilling was carried out by Huber Leitungsbau.

The urban environment necessitated the drilling to be executed with utmost precision. The pipeline had to be installed at the correct depth under the streets of Stäfa and the drill had to reach the exit point with minimal deviation. The hard rock in which the drilling took place also posed a challenge for this project. Additionally, the job took place close to the Stäfa train station, requiring the crossing of four train tracks and a pedestrian tunnel.

For this challenging task, an S-shaped trajectory was designed. The drilling was required to make a 17° right turn beneath the train tracks, followed by a 12° left turn to follow the street above. This ensured the drill reached the exit point with the correct direction.

To provide absolute precision, Brownline surveyed this drill with the Drillguide Gyro Steering Tool. In the very hard rock layers, the Drillguide GST provided certainty by tracking the exact position of the drill bit with real-time measurements. The Drillguide GST is not influenced by external factors. This makes the system ideal for drilling in urban environments with extensive above-ground and underground infrastructure.

As the drill head approached the exit point, an additional surface-level check was conducted using Brownline's GPS track. The GPS track equipment is very compact, making it suitable for use in a project such as this one, where there is limited space on the surface.

Thanks to Brownline's service and high-tech measurement systems, the cast iron water pipeline was installed accurately and with minimal disruption under the center of Stäfa.