A railway possession during the late May bank holiday means a key stage of the London Bridge redevelopment can now start.
The £1bn project to redevelop London Bridge station made the wrong sort of headlines earlier this year when restricted concourse space brought about by the construction work led to overcrowding. British Transport Police had to be called in to maintain order as crowds 50-deep were pushed up against ticket barriers during the busy evening rush hour. This in turn led to a public dressing down for Network Rail from London Mayor Boris Johnson.
Network Rail project director for London Bridge and Bermondsey, Laurence Whitbourn argues that such scenes are difficult to avoid when conducting major construction work at a busy railway station. He also seems confident that these problems will become a thing of the past when the next phase of the project reaches completion.
“The work we are doing now is probably the most important phase of the project from the station’s point of view,” he says. Once it is complete, two-thirds of the new Wembley-Stadium-sized station concourse will be finished, reducing overcrowding at platform level.
As reported previously in NCE, the redevelopment involves the staged demolition of a series of Victorian viaducts to create space for the vast concourse that will sit in the middle of the station. These viaducts were constructed haphazardly as the station grew in the 19th century, adding to the complexity of today’s engineering challenge.
“Effectively we’re cutting a slice through [the existing station] for the concourse, but to the east and west of that, all of the arches are being retained,” says Whitbourn. “When you go underneath you realise the whole thing was built in a series of stages back in Victorian times and was not fully coordinated. Some of the structures just abut each other, so it’s a very complex job.”
In the finished configuration, buttress walls will support the original Victoria viaducts at the east and west of the site, while eight giant bridge decks sat on concrete crossheads will span the newly cleared central concourse section. Fifteen new platforms will sit on these eight bridge decks and passengers will be able to exit down into the uncluttered concourse by escalator before leaving the station or proceeding to the London Underground station through new, wider passageways at the western end of the station.
The other main objective of the project is to change the station from one that has nine terminating tracks and six through tracks to one that has six terminating tracks and nine through tracks. It forms part of the £6.5bn Thameslink project which aims to improve the number of Thameslink trains passing through the station every hour.
The easiest way to imagine the project is as a band of demolition and reconstruction passing through the central section of the station’s footprint from its southernmost side near St Thomas street to its northernmost side near Tooley street. This has been staged to coincide with a series of railway possessions during public holidays. The southernmost platforms 16, 15 and 14, were the first to be taken out of action to start to make way for the first of the three bridge decks of the six terminating platforms on the south side of the station. Technically, there were 15 platforms in the old configuration but the existence of a passing loop, meant the station always counted 16.
The work front then moved to platforms 13 and 12, and then platforms 11 and 10. The first phase of the project finished when all of the terminating platforms were completed earlier this year and train services began to terminate at newly configured platforms 10 to 15.
Whitbourn says the main reason for the overcrowding in January was the fact that passengers currently exit these terminating trains through a concourse at the base of the Shard at the western end of the site. The problem is that this concourse was not designed for such large numbers of passengers.
“The terminating platforms in their final layout will have escalators down to the main concourse,” he says. “Currently everyone is coming off into the Shard concourse which is what gives us the restriction. We have an interim stage with a concourse which is not designed to take the permanent traffic. The numbers work quite well during normal service but when we go into perturbation, the normal concourse becomes overcrowded quite quickly.”
Because the terminating platforms are now complete, the construction work front is now situated further north in a central core running from east to west though the centre of the station footprint, with live trains running either side.
One of the principle ways in which the construction team has freed up rail capacity as platforms and rail lines have been demolished is to prevent some services from stopping while the work progresses. In the present phase, through trains to Charing Cross station do not stop at the station and run on a single up/down track, also known as the “up-passenger loop”. This allows Charing Cross services to pass through the station more rapidly.
A track possession over the late May bank holiday moved this track to the north of the site from a position alongside the old platform 7 to a new position alongside the yet-to-be-demolished platforms 1,2,3 and 4.
“That was live up until the end of May so that meant we couldn’t progress demolition but we’ve now moved that line across to the other side of the site meaning that’s freed up all of that area for us to do demolition.”
This demolition work, which was in full swing when NCE visited the site in late June, has in turn freed up space for Phase 2, allowing the two bridge decks for platforms 7, 8 and 9 to start to be constructed. Platforms 7 and 8 will run on one bridge deck while platform 9 will share a bridge deck with a services spine.
This phase will also include the construction of four new viaducts to carry the trains served by these platforms out of the west of the station and on to central London. The first of these, known as the station approach viaduct extension, will pass over some of the retained Victorian elements at the west of the site and join the ends of the new platforms to the station approach viaduct. Trains will then pass over what is called the railway approach viaduct, a structure spanning the bus station at London Bridge’s westernmost tip. This in turn will connect to the Borough viaduct spanning Borough Market and built by Thameslink earlier in the project.
Network Rail scheme project manager, interfaces team, Janey Bell says: “What that does is create a new path for the Charing Cross tracks and that frees up space in the middle of the station for our dedicated Thameslink platforms.”
The construction team has made innovative and cost-effective use of polystyrene infill to build up the levels of the retained and buttressed Victorian arches at the western end of the station for the station approach viaduct. “It’s the polystyrene we all know from coffee cups but under compression it’s very strong,” says Whitbourn (see video below).
These viaducts and platforms 7, 8 and 9 are due to be finished in October. Then the railway systems team is scheduled to put down track ballast and signalling equipment by Christmas so that a more frequent Charing Cross service can begin to use these platforms. However this service will still not stop at the station. More significantly still, two thirds of the new concourse below the viaducts will be complete by August 2016 allowing passengers using this service to alight at the station for the first time since early 2015. This will also ease congestion in the stressed Shard concourse.
Bell thinks progress has been rapid. “In December last year, before the blockade, we had Charing Cross lines running where we are building the new bridge decks now,” she says. “Since then we’ve demolished the platforms we’ve demolished the arches down below and we’ve done our piling and reinforced concrete works.
“We’re getting ready now for the steelworks to go in for the new platforms and then on 5 January next year  we will have trains running over the new bridge deck structures in that area. It’s amazing to think that we’ll have them running over the new structures in just over a year.”