2017-10-26

The world´s longest city tunnel – A real hard rock challenge

17 kilometres of Stockholm’s new outer ring road to be under ground

Like other fast growing cities, Stockholm has long fought increasing traffic congestions resulting in longer commuting time as well as air pollution and other environmental problems.

The main artery between southern and northern Sweden virtually goes through Stockholm city, and the Baltic Sea and Lake Mälaren effectively lead much of the commuting into the very same road.

Way back in the 1960s, a regional plan for the future infrastructure of Greater Stockholm was outlined, proposing three concentric half-circles to the north, west and south. The eastern outskirts, facing the city’s environmentally sensitive archipelago, were essentially untouched.

Environmental contradictions

Through the past half-century traffic has multiplied many times over, some of the ideas have been more or less realized. But, in spite of the early insight, much of the outermost semi-ring road got stuck in a seemingly endless series of differing political opinions.

Beyond the temporary disturbances during the construction phase, the main reoccurring discussions relate to the air quality in such a long tunnel, but also to more fundamental issues”, says Niclas Johansson at Sigicom’s Stockholm office. He explains:

The political majority now agrees that Stockholm and the entire country really need the new road to keep growing and flourishing. While environmentalists, inside and outside the parliament, keep insisting that the money would be more wisely spent on the buses and extensions of the existing underground system.

Monitoring noise and vibrations

In the autumn of 2014, at last, the Swedish minister for infrastructure was able to conduct a groundbreaking ceremony and, unless further political disputes evolve, the project is now estimated to be finalized around 2025.

“Parts of tunnel system will run 65 meters below ground, and the Scandinavian bedrock is old and hard”, says Niclas Johansson. “Over the next few years huge amounts of rock will have to be blasted away, and monitoring the resulting vibrations, noise and other environmental impact will be required.”