Invisible investment
PAUL STEPHEN scratches beneath the surface of Network Rail’s work on the southeastern end of the Elizabeth Line and discovers that the money being spent now will bring benefits for decades to come
RAIL scratches beneath the surface of Network Rail’s work on Crossrail’s southeastern arm at Abbey Wood.
Apart from the 26 miles of tunnels constructed by Crossrail Ltd beneath central London, Network Rail is responsible for delivering £ 2.3 billion worth of work above ground, where the Crossrail route utilises parts of the existing network.
This includes modifying 28 existing stations, and is largely concentrated on enhancing the Great Eastern Main Line between Liverpool Street and Shenfield, and the Great Western Main Line between Paddington and Heathrow Junction and Reading.
It also includes upgrading a much shorter section of track on Crossrail’s south-eastern arm, however, running alongside the North Kent Line from the Plumstead eastern tunnel portal to Abbey Wood, where a new terminus station is being built for Crossrail, to act as an interchange with Southeastern’s existing through services.
Work began in 2013 and is rapidly nearing completion, on what is effectively a threemile construction site in preparation of the first Elizabeth Line services, which will run on this section in December 2018.
For two miles to the west of Abbey Wood station, the two-track formation of the North Kent Line needed to be widened into a fourtrack corridor to accommodate the two new Crossrail tracks, emerging from Plumstead tunnel.
To create sufficient space, the North Kent Line tracks had to be moved five to six metres further south for a distance of two miles, and then gradually slewed from their new positions to reconnect with the old alignment, approximately a mile to the east of Abbey Wood station.
The task of widening the alignment was complicated by the high water table of the surrounding land, which used to be marshland until it was drained and then urbanised by Victorian developers during the 19th century.
NR’s solution was to drive 1,800 concrete piles up to nine metres into the ground, to support wide concrete ballast slabs, placed on either side of former two-track alignment.
This was expensive as well as challenging, and almost three quarters of the £150 million budget spent by Network Rail on this section of Crossrail was invested in building these earthworks and drainage courses.
Finding adequate room for four tracks was also problematic for NR’s engineers, requiring the demolition of several endof-terrace properties and the compulsory purchase of some sections of adjoining gardens.
“The single biggest challenge has been
The single biggest challenge has been building this through a housing estate. Peter Hume, Senior Programme Manager, Network Rail
building this through a housing estate,” explains Network Rail’s senior programme manager Peter Hume. “There are 2,000 residences that encircle a site over three miles long.
“You can’t see where a huge amount of our investment has gone, as it’s been done below ground level to solve that drainage problem.”
The project also required a great deal of logistical planning. Trackwork had to be carefully carried out in phases, in order to support the early establishment of a railhead and temporary logistics centre at Plumstead tunnel portal for engineering trains, used for the ongoing fit-out of the tunnels and stations by Crossrail contractor ATC.
This end of the three-mile worksite was, therefore, completed first, so that ATC could stable its concreting factory train at Plumstead, and an overhead gantry crane could be erected above sidings to supply engineering trains used for trackwork, and all other necessary works, some of which are ongoing.
A £ 30m permanent depot will eventually be built here for maintenance rail vehicles, which will be operational in early 2019.
It was also important to conduct the work in stages in order to keep Abbey Wood open, a station used by some 4,500 people during the morning peak.
With the North Kent lines moved south, both of Abbey Wood’s original two platforms have been demolished and rebuilt, to form two new island platforms.
The southernmost of these was completed first, and a temporary station building erected so that Southeastern services could continue to serve the station while work
What’s been carried out here has been so extensive that no further work should be necessary for at least 20 years. Peter Hume, Senior Programme Manager, Network Rail
began on the northern island platform, and the new station building itself, which is elevated above all four running lines.
Disruption has therefore been kept to a minimum, adds Hume, apart from a series of brief full-line possessions, an unavoidable measure due to the close proximity of fully energised 700V DC lines to the building works. The scope of the trackwork means that future enhancement and renewal work should be kept to a minimum, however, limiting the need for any future possessions.
“The project has taken four years. We could have shut the station completely and diverted Southeastern trains to do it faster, but the industry view was that Abbey Wood is too busy to close. To get round that we developed a strategy using conventional line possessions that allowed people to carry on travelling, and with minimal impact.
“100% of the railway assets have been replaced. What’s been carried out here has been so extensive that no further work should be necessary for at least 20 years. This section of track will be maintenance and renewal free for a long time.”
The station design itself had to cater for up to 20,000 people using Abbey Wood in the morning peak, with half of those interchanging to Elizabeth Line services, and the rest consisting of local journeys.
Due to the local drainage problems, a further £ 20m had to be spent on building the extensive foundations and concrete support structure required beneath the elevated concourse, while £ 25m is being spent on the concourse itself. The primary contractor on-site leading all the works is Balfour Beatty.
The station’s distinguishing feature is a gently curving roof shaped like a manta ray, formed by glulam (glued manufactured timber) wood panels installed by Austrian firm Wiehag, that are covered in zinc. Beneath the roof, the station building has been constructed using 31 tonnes of steel beams and girders.
It makes a bold architectural statement, but the new station has also been designed to deliver more functional improvements to the economically depressed local area, via its integration with adjacent flyover, Harrow Manorway (the A2041).
This elevated road has made walking
around the area difficult, and has formed a visually intrusive physical barrier through the area since its construction in 1975.
New staircases, walkways and a granitepaved concourse will dramatically enhance pedestrian access between the areas of Thamesmead and Bexleyheath located on opposite sides of the railway, while stimulating more than £10m investment from local councils on improvements to the surrounding urban area.
It has also had a regenerative effect on Abbey Wood, with a new supermarket already opening close to the station, and 1,500 homes under construction nearby. Meanwhile, planning permission has been granted for a public plaza, library and a further 220 new homes.
The new concourse will also contain retail units to closely resemble a high street, reinforcing the station environment’s feel as a thoroughfare linking the two communities.
Now that the external structure is complete, the emphasis will shift onto the station building’s internal fit-out, before it is ready to open to Southeastern customers in October.
That month will also mark the end of Network Rail’s involvement in the project, as the Crossrail island platform and running lines are handed over to Crossrail Ltd to begin dynamic testing and commissioning, in advance of the full station opening in December 2018.
Matt Steele, Crossrail Programme Director at Network Rail, concludes: “This is one of my favourite sites as it’s an opportunity to leave something iconic and make a bold architectural statement. It’s also a rare chance to build some all-new railway.”