Longest flush drilling in the electricity sector in Switzerland

The electricity supply for the city of Chur is based on a ring-shaped power grid with four substations. The 60 kV ring supplies the city of Chur, but also has regional significance, as Arosa and, if necessary, Lenzerheide and Churwalden are supplied via this ring.

The last section of the 60kV ring between the Quader substation and the Sand substation must be renewed because it no longer meets current requirements. The existing cable line is too small and can no longer reliably transport the required amount of electricity. In addition, the cables run in old cable cover stones that are in need of renovation and have been badly damaged over the years. A renewal is necessary to ensure long-term security of supply.

A tensile force of 300 tons is required to ensure the replacement power line, a 1000m borehole that runs 20 to 70m below the ground in the rock (Grisons slate). After completion, the natural stone wall and the vineyard on Planaterrastrasse as well as the plots in the Sand area will be restored. The implementation of the project will ensure the supply of around half of the city of Chur and the Central Grisons region.

What is a flush drilling?

The flush drilling – also known as horizontal flush drilling – is a method of laying pipes, cables or other lines underground without having to dig large areas. Instead of using traditional excavations, this method involves driving a drill head through the subsoil. With the help of a drilling fluid, a mixture of water and bentonite, the excavated material is loosened and transported to the surface. Up to 300 tons of traction are required for this drilling, which is around 1000m long.

sustainability in focus

Wash drilling offers numerous ecological and practical advantages:

Minimal impact on the environment: In contrast to open excavations, the natural landscape is hardly affected.
Reduction of emissions: Since fewer heavy machines and trucks are needed for excavation, CO₂ emissions are reduced considerably.
Protection of habitats: Green spaces and adjacent ecosystems remain largely intact.
Protection of infrastructure: Roads, sidewalks and existing pipes are not damaged, which minimizes later repair costs.