Transforming Abbey Wood into Crossrail’s southern terminus demanded a meticulous and multi-disciplined approach from main contractor Balfour Beatty in both design and construction.
Project: Abbey Wood station – Crossrail southern terminus
Contract value: £130m
Main contractor: Balfour Beatty
Start date: January 2014
Completion date: December 2018
When Abbey Wood station was first built in the 1850s it was nothing more than than a small suburban station on the outskirts of south-east London.
It would have been seen by many Londoners as a station to pass through while getting away from the chimneys and crowded conditions of the capital.
Fast forward nearly 170 years and the station is in the midst of a transformation and is about to become one of the capital’s most important stops.
As the southern terminus for Crossrail, it will be the end of the line for London’s newest rail project. Connecting with the existing Southeastern rail line, which stretches from Lewisham’s St John station to Rochester, it will be the gateway for many of Kent’s commuters into central London.
Balfour Beatty is rebuilding the station that straddles the Greenwich and Bexley border and reconfiguring the track to accommodate the Elizabeth line, the official name for Crossrail. With the revamped station’s grand opening scheduled for early autumn, Construction News was invited down to the tracks to check out progress on the £130m project.
The project outline
Balfour Beatty won the contract to transform Abbey Wood station in 2013.
With a team consisting of many of those that had worked on the development of the East London line, Balfour Beatty was brought on board with an ECI contract from Network Rail.
While the revamped station belongs to Crossrail, responsibility for its delivery and the related infrastructure was handed to Network Rail, which oversaw procurement and the project management of the scheme.
Balfour Beatty construction manager Andrew Bradshaw, who managed the Carillion / Balfour Beatty joint venture for the £363m East London line, has led the scheme since the contract was awarded. His team is currently well into the process of constructing the massive new centrepiece station for Abbey Wood to give travellers access to the Elizabeth line towards central London and out towards Kent.
The massive curved structure and its concourse will replace the modest brick structure and become the centre point for the area’s regeneration.
But Abbey Wood is a lot more than just a building project.
“It would be a real tall order to do this with steel, but with timber it is a lot more flexible and has the same design life as the station”
Andrew Bradshaw, Balfour Beatty
Previously served by only two tracks – on Southeastern’s North Kent line – the contractor has had to widen, realign and lay more than 3 km of track so the North Kent line could be moved to accommodate the Elizabeth line when it comes into operation next year.
Add to this the need for new signalling, the repositioning of points, construction of new bridges and a substation, and installation of some of the only overground electrified lines in the South-east of England, and it’s clear why the planning and co-ordination on this project has had to be meticulous.
Three-quarters of the way through the build, the station is on schedule for its October opening.
The manta ray
When Abbey Wood is finished it will be the biggest completed station project by value within Network Rail’s portfolio. But it has not been the only station built during the lifecycle of this project.
To ensure that Southeastern services could run on the North Kent line, a temporary station needed to be built to serve passengers as construction took place.
The temporary ticket office, which by the end of its operation would have stood for three-and-a-half years, was built and fitted out offsite in Nottingham by prefab builders Thurston and includes cash machines and ticket facilities.
Network Rail’s Crossrail senior project manager Peter Hume says: “You might call it a temporary station, but in truth the temporary station [has better facilities] than a number of permanent stations.”
So high is the spec for the offsite ticket office, Network Rail is currently considering taking it out next year and using it as the ticket office for a smaller regional station.
The second more permanent station, through which millions will pass from 2018, is just months away from completion.
Balfour Beatty Abbey Wood timber roof structure 6
The design was chosen by Crossrail and local authorities, and nicknamed the ‘manta ray’ due to its glulam timber-formed shape. Manufactured by Austrian firm Wiehag, it is the same material used on Canary Wharf’s Foster & Partners-designed Crossrail Place station.
“It would be a real tall order to do this with steel, but with timber it is a lot more flexible and has the same design life as the station,” Mr Bradshaw adds.
The manta ray will cover a massive concourse and Mr Hume hopes it will become a defining landmark. “This is a flagship station for us and will be the centrepiece for the regeneration of the Abbey Wood area,” he says.
The project is not solely about the station. “This is an extraordinarily multi-disciplined project,” Mr Bradshaw says.
Taking in civils, signalling, track work and pure building work, the contractor has had to draw on a wide range of skills from design to construction, which began the moment the work was procured.
“The concept of ECI has been used before but usually using the contractor as a consultant providing buildability input,” Mr Bradshaw says. “On this one, however, Network Rail said start designing the job the way you want to build it.”
At the time Balfour Beatty won the job, it owned design consultant Parsons Brinckerhoff, which gave it extra capabilities to take the contract through the design phase. It also meant that Mr Bradshaw and his project team could be involved at the earliest possible point, something Network Rail’s Mr Hume believes has been fundamental to its smooth delivery.
“Having that single contractor planning the job early on and [working up the] strategy on how they want to do it, and seeing through the build, has worked really well,” Mr Hume says. “We’ve had such a stable team throughout, with construction managers and designers sticking with the project all the way through.”
“The concept of ECI has been used before but usually using the contractor as a consultant providing buildability input”
Andrew Bradshaw, Balfour Beatty
And this range of capabilities has stood them in good stead through construction, too, with Balfour Beatty being able to keep most of the specialist work in-house. “We see this as a real showcase of our capabilities because [with all these] disciplines involved, we have people that can deliver,” Mr Bradshaw says.
He believes using the contractor’s in-house specialist teams such as Balfour Beatty Ground Engineering, which was responsible for all the piling work, has leveraged a joined-up approach on what is a complicated scheme.
“We have subcontractors lower down the chain but at management level it is with our own specialists within those fields who could be part of our internal joint venture arrangement,” Mr Bradshaw says. “On a project like this, being a one-stop shop is extremely helpful.”
The phasing of the Elizabeth and North Kent lines meant tracks could not be realigned simultaneously (see diagram below; click for larger image). To ensure the station could serve the Elizabeth line by 2018, the North Kent lines had to be rerouted first (middle diagram).
A conventional approach would have seen platforms serving the Elizabeth line and North Kent line built and then the track being realigned to fit in with this.
Balfour Beatty Network Rail realignment diagram
But Crossrail’s tight delivery deadlines meant Balfour Beatty needed to hand over a large part of Crossrail track by May 2015 so Crossrail’s work trains could carry out fit-out work and lay track in the tunnels.
However, construction on the platform that would eventually be served by a realigned North Kent line had not been finished. As a result, the team had to come up with a temporary solution that would allow space to be created for the Crossrail lines, but would still mean the North Kent lines could serve the temporary station so construction on the main platforms and station could take place.
“One of the major challenges was in planning how to do this,” Mr Bradshaw says.
The solution was to add a temporary dog-leg to the north Kent line to create the area Crossrail needed and then later re-route it back so it could re-join its original alignment. This saw Southeastern services taking this built-in swerve for a number of months.
The great sink
When the original rail line was built more than 160 years ago, the Victorian engineers faced a problem. A site that was originally a bog meant ground that was hardly ideal for laying tracks.
To overcome this, the Victorians built an embankment for the lines, which was built up over and again over the years as it continuously subsided.
After years of rebuilding the embankment, and the help of more modern ballast methods, the ground under the original Kent line is a lot firmer now. The ground on which the Abbey Wood project aimed to expand onto, however, wasn’t.
“While the embankment had been squished down over years and was solid, the area for expansion was virgin ground,” Mr Bradshaw explains. “If we were to just build up fill and put some track on it, over the life of the project the track would settle and we are talking about settling by 800 mm.”
In total the project has received 1,200, 9 m driven piles under the track, with each pile being topped with a metre-thick concrete cap. Meanwhile, BBGE has installed 600, 25 m-deep piles under the station.
Network Rail’s Mr Hume says that a large part of the construction cost has gone into the ground engineering that will keep the track and the station stable.
Once Abbey Wood’s North Kent line platforms were completed last year, Balfour Beatty was able to carry out the full realignment of the Kent lines through the station to make way for the Elizabeth line (bottom diagram).
This final realignment was carried out in a 52-hour possession, with 500 m of new track laid as well as the installation of related infrastructure. “There’s a lot of associated signalling work to install signal posts and commission the signals all ready for 4am [on a] Monday morning,” Mr Bradshaw adds.
Islands in the stream
As is generally the case on rail jobs, the speed and success with which work can be delivered is often dependent on the degree of track access. This was no different on the Abbey Wood project, with Southeastern’s North Kent line a crucial artery for Kent commuters.
“Obviously we have to keep trains running on weekdays and there is a limit to how many possessions you can do, so that brought in a very complicated staging strategy,” Mr Hume says. “We didn’t want to close the station – the whole philosophy was to try and keep normal services going.”
“We have to keep trains running on weekdays and there is a limit to how many possessions you can do, so that brought in a very complicated staging strategy”
Peter Hume, Network Rail
To ensure possessions caused as little disruption as possible, the contractor created what was effectively an island site, just metres away from passing services.
When the current was turned off at night, the team was given just two hours in which to load plant and materials on and off the island. “We would wait ready for when our two-hour window came and then we load out and do any work we could fit into that period; it was a very intense period of activity,” Mr Bradshaw says.
But the logistics of getting equipment onto the island was only half the job.
Balfour beatty abbey wood 7
Once working on the island, systems needed to be followed rigidly for worker and commuter safety. To ensure this, all plant equipment was rigged with safety mechanisms that could prevent machines moving into the path of an oncoming train.
“You also have to ensure very close communication between the guys marshalling the plant and those operating the trains,” Mr Bradshaw adds. “This was done through headsets where they could talk all the time.”
With all the planning that has gone into the scheme, Balfour remains convinced that ECI is proving a critical factor in the successful delivery of Abbey Wood’s new station.