At first glance, it would be easy to assume that the photo above had come from one of Britain’s remaining mines. Indeed were it not for the presence of the ubiquitous orange jacket, it would be equally easy to assume that the photo was from a different time.
In fact the location pictured is far closer to home – it is a photo of Oxford Street.
With Tottenham Court Road Station closing to Northern Line passenger traffic today, it is perhaps inevitable that much of the media coverage will focus on the disruption this will cause. To a certain extent this is fair, as travelling to Tottenham Court Road is a key part of many people’s journeys. As the photo above suggests, however, the work underway at Tottenham Court Road is greater and more complex than many people realise. With that in mind, it is probably worth us returning to the station site and taking a look both at what has been going on there, and what will be happening during the upcoming closure.
Tottenham Court Road is a station that is now almost uniquely unsuitable for the role it has to play. Standing at the heart of London, the station’s surface access, ticket hall and passageways are now inadequate in relation to the role it plays.
A drastic reworking of the station’s sub-surface layout has long been needed and it is this that is now underway. By 2016 the station will have a completely new ticket hall, new access tunnels, lift shafts and escalators. It will also connect through to the new Crossrail Tottenham Court Road. It is a project this is proving a unique challenge.
One of the most obvious problems has been siting the construction. Digging the lift shafts, escalator boxes and access points for sub-surface construction requires space – and space is something that is at a premium at Tottenham Court Road. It was the need for this space that led to the demolition of the Astoria and other buildings around Centre Point (timelapse footage and photos of the TCR demolition work can be found here). That, combined with the closure of Charing Cross Road and the seemingly endless blue hoardings that face onto Oxford Street give the illusion of a large construction site.
Interestingly, however, it’s actually a site that is far more compact than it seems. As the photos below show, now that they’re well underway the construction work, spoil removal and other works are actually very tightly confined. Thanks to the variety of works underway it is an interesting site to watch in action, with diaphragm wall machines, Bentonite tanks and various other site machinery all working in close proximity.
Indeed the sheer value of space in the Tottenham Court Road area has also obviously had an effect on the construction techniques being used. In Yerkesian style, oversite construction is clearly a key part of the design. This is particularly evident in the new escalator box, where the piling and support works are obviously designed to support significant above-ground weight.
Another problem the station reconstruction has faced has been the utilities that run through the area. A large (and decidedly Victorian) sewer pipe runs down Charing Cross Road and the diversion of this, as well as a cast iron watermain, gas pipes and power and telecoms cables was the cause of much of the visible disruption on Oxford Street in recent months. A non-simple task already, this proved even more tricky due to the proximitity of all these utilities (some of which were sitting directly on top of each other) and the age of some of them. The fragility caused by age effectively meant that even though some were not directly vulnerable to the excavation work, they had to be relaid as there was a risk that the general movement of the earth the construction would produce would cause them to crack.
Whilst the above gives a good idea of what has happened so far, the question remains as to what comes next – what precisely it is that requires the Northern Line be closed at Tottenham Court Road for the coming months.
The answer to this actually lies in the station’s complex history. The station has been through three distinct iterations. It was first constructed for the (now) Central Line and opened in 1900, then “Oxford Street” station opened on the (now) Northern Line in 1907. This was effectively merged with the existing Central Line station in 1908, its above ground buildings eventually disappearing with the construction of Centre Point. Finally, like many stations, Tottenham Court Road was reworked to include escalators in the 30s.
As the above paragraph suggests, beneath the surface, Tottenham Court Road station is thus a twisting and tight network of tunnels and passages – both for people and trains. This is a network that will be further complicated by Crossrail, which will be driving its own tunnels through the site in the coming years. Indeed the looming presence of the Crossrail tunnels is something that is having a noticable impact on the construction of the new Northern Line escalator box.
Construction of this has reached the point where the dig is now just above the height of the incoming Crossrail tunnels. This means that the escalator box is not, as the name might suggest, actually cuboid. At its lower levels it has to be higher on the northern side and carry a 30 degree incline down to the south in order to allow the Crossrail tunnels to pass through the area untroubled. Its an interesting engineering challenge as those working on the site are happy to admit, as the growing incline makes working in the box with heavy machinery more difficult than would be expected.
Away from the escalator box though, it is the new lift shaft that will descend from the new ticket hall that is largely responsible for the upcoming disruption. It’s a vital part of the new design, not least because it will provide step free access to the Northern Line platforms. There is, however, a problem – at the level of the Northern Line tunnels, there isn’t actually enough room for it to sit between the two.
What will happen in this closure, therefore, is a rather delicate procedure. In crude terms, the two tunnels will be “nudged apart.”
Obviously, its a safe exercise, but one that requires some rather creative engineering. Without going into excessive detail, effectively the lining on one side of each platform tunnel will be modified and reinforced. This will change the profile of the platform tunnels slightly, allowing the lift shaft to be driven down between the two and completed. It is a complex procedure and carrying out this exercise with the Northern Line platforms still open to passenger traffic would likely have taken years – hence the decision to close.
All the above hopefully gives some idea into what is currently taking place at Tottenham Court Road. It is in an incredibly complex project, and one which is crucial to the future of the Underground network. It is also a project that, undoubtedly, has caused plenty of disruption and will certainly cause more in the months to come. Ultimately, however, it is important to remember that there is a reason for it – and that there is a lot more going on behind those blue hoardings on Oxford Street than it may sometimes seem.