Underneath the ground in London is one of the most complex networks of utility lines as well as rail systems in the world. Merely navigating the treacherous web of lines and tunnels can be a weeks’ long process, but when you couple that with the idea of adding a new rail system, affectionately known as the Crossrail, then you come across a logistical challenge that can put nearly any engineer to an early retirement.

For any Londoner, the underground projects that have been taking place throughout the city are a well-known fact. It’s not easy to avoid the construction, hear the sounds and the sights of equipment coming and going, and feeling the effects through delays in commutes. Yet while all of this has been going on for years to upgrade the commuter system (in which the oldest part of the rail system is 149 years), the most challenging phase of the project has finally come to fruition: the Crossrail.

A Look At the Challenge

On the surface, it might not seem as though there is much to worry about by placing a new rail tube underground. After all, other major cities around the world have been doing this for years without a great deal of fuss or fanfare, so what is the challenge?

The first challenge is understanding that the deepest point of the new rail system will be 67.4 meters underground. For any Londoner who knows about the structure of the buildings above ground level, there is an intricate and often seemingly random network of cellars, basements, and sewers underground, not to mention the water mains and other structures. Add in gas lines and electrical conduits and finding the most reasonable and logical path through them becomes a greater challenge for engineers than merely mapping out a path and beginning the tunnelling process.

The chief engineer on this project, Chris Dulake, states that this fundamental challenge is the toughest part of the job. He said, “It’s quite a challenge to plan the alignment of the tunnel when you’re threading your way through all the tunnels and services.”

Indeed. To put this into a little more perspective, the new Crossrail line will come within one meter of an existing tube, or tunnel. When one is speaking in terms of a major rail system and network, one that carries millions of passengers throughout London annually, the potential for trouble is exacerbated. It’s not to be taken lightly.

See a map of where the tunnels will be dug in this BBC article here.