Wonderful Engineering

How Deep Does London’s Construction Go?

London is one of the oldest cities in the world. Due to the Great Fire, civilian bombing in World War II, subsequent reconstruction and many other mass level uplift projects, it has become hardly recognizable as the muddy town from the middle ages that was full of dust in the summers and sticky mud in the winters. We know that a city as grand as this might rest on firm foundations and deep underground drainage system to function well. We have seen how Tokyo has a colossal system in place, but not many of the cities face the kind of water problems Tokyo does. One related question that comes into mind while thinking about drains and underground tunnels is that how deep a city goes counting all kinds of construction underneath the belly of the giant?

Surely there are deeper places than the subterranean Underground with a host of basements, bunkers, water pipes and sewers present underneath. An attempt to summarize significant underground civil work in the form of a map would make the job easier so here it is:

It also plots the under-consideration Thames Tideway Sewer Tunnel as well. Studying it, we can see that the depth varies from location to location and project to project. For example, the Tube’s average depth is 27 meters. But in some places it plunges deeper than three times its average depth with the under-construction Bull and Bush station in Hampstead reaching almost 67 meters. However, even that station isn’t the deepest part of the English city. The first place goes to Lee Tunnel, which is a relief sewer that slopes down to an eventual 80 meters beneath Beckton. Just like you expected, there is a string of deep underground construction throughout the city. The makers of this map left bunkers, service tunnels, tram tunnels for the sake of clarity because they don’t dip that much, and there are just too many!