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Closing the circle

Work is progressing to extend the East London Line to Clapham - including new permanent way along a short but important link in Transport for London’s Overground metro network. Jon Masters reports.

Birse Metro is currently carrying out groundworks for a the £25M, 1.3km new build section of East London Line (ELL) in Lewisham. This is work package one of the line’s £75M western extension to Clapham Junction, a connection to complete Transport for London’s (TfL’s) Overground metro network.

The new section of track will connect the existing East London Line at Surrey Quays to the commuter line which runs into London from north Kent at Peckham.

Two further £25M work packages will involve Network Rail’s contractor Carillion connecting the new 1.3km of track south of Surrey Quays to the existing South London Line and remodelling platforms one and two at Clapham Junction to take Overground trains.

Orbital route

When complete, the London Overground metro network will form an orbital route around London with links to Stratford in the east, Watford to the north and Croydon to the south (see box).

Extending the ELL through Lewisham has its own engineering challenges, due in part to the line’s significance for local regeneration. Planning designation for the vicinity has changed from light industrial to residential in recent years so Mott MacDonald’s designs have been influenced accordingly. Contribution to the design costs has come from Lewisham Borough Council with the possibility of funding from developer Renewal.

“Knowledge of the effects of railways on development and regeneration tends to be a mixture of high end academic study and simply what we see happening after new lines are built. [Developer] Barratt cannot build houses fast enough in the vicinity of ELL phase one,” says London Rail chief operating officer Howard Smith. London Rail is the TfL directorate responsible for creating the Overground network - and oversees the operating concession.
Birse Metro’s work includes provision for a future station at Surrey Canal Road to be finished later and funded in part by Renewal. The station is not considered necessary right now, but will be as demand rises.

“We are doing as much as we can while we can at the station, particularly with piling work, ahead of completion of utility diversions”

Alex McTaggart, TfL

“If Surrey Canal Road was opened now it would get very little use,” says Smith.

“The point at which the station will go in cannot be predicted, but will be triggered by a number of factors at a later stage including development and general crowding of services,” he says.

So for the time being, the structure of the station concourse at street level and the substructure for the platforms above will be all that is built.

“The change of planning designation has influenced the designs by increasing the required permeability of movement,” says London Rail ELL phase two project manager Rob Jones.

167 piles

Birse has 167 bored piles to install to support the station structure and the 27m single span steel and concrete composite bridge that will carry the ELL over Surrey Canal Road and its footpaths.

The bridge’s north abutment will be a reinforced concrete box to be used as a subway. The load bearing front wall of the subway box which will be supported on two groups of four 1,200mm diameter piles of 20m depth; the back wall of the box on a row of six 750mm diameter piles, abutting a reinforced soil embankment.

At the southern end of the bridge, its piled abutment wall will provide the end support for the concrete beam and slab roof of the station concourse above.

The roof slab will also sit on two intermediate rows of reinforced concrete columns on 750mm diameter piles, and a further contiguous bored pile wall forming a diaphragm between the station structure and earth embankment. Above and immediately south, 64 piles, also 750mm in diameter, will support the station’s 80m long ground slab - with upstands in readiness for taking concrete platform planking.

Birse has a tight construction programme as all construction work must be finished ahead of the start of the Olympics in July next year.

Critical path

Piling work is on the programme’s critical path. More so are diversions of high voltage cables obstructing the southern bridge abutment and station concourse; and a 1m diameter medium pressure gas main in the way of the Rollin Street subway.

“We are doing as much as we can while we can at the station, particularly with piling work, ahead of completion of utility diversions,” says TfL’s ELL construction manager Alex McTaggart.

Southern Gas Renewals’ contractor Morrison, set the task of carrying out this diversion while the gas main remains live, has called in a Belgian specialist for the job. Work has been underway for almost three months and McTaggart is hopeful of an imminent finish to the gas diversion, clearing the way for the subway work to follow.

Despite all this, TfL’s director for London Overground Infrastructure Peter Richards says the biggest challenge has still to come with integration of rail, power and Network Rail’s work to connect with existing lines.

There is an air of confidence about getting everything finished on time, however. Smith says Lewisham Borough Council has helped with rapid approval of notices about allowable noise levels to allow work to take place within 48 hours of a request being made. Strong local and political support for the rail link and station he cites as significant.

The ELL extension contractor for signalling and communications is Invenys.

Balfour Beatty Engineering Services is installing power connections. Both, with Birse Metro, worked on phase one of ELL. Overground trains should be running between Surrey Quays and Clapham from December 2012.

 

Overground upgrade

Much of TfL’s Overground network runs on Network Rail track in London. Since 2008, this shared network has undergone refurbishment by Network Rail teams, with upgrade of signalling, station and communications systems.

Network Rail’s input - including 23% of the £326M Overground costs - is part of its £700M 2012 Programme. This is now virtually complete a year ahead of the Olympics, having included all station works and a new freight loop at Stratford, as well as resignalling of the London main line network shared with the Overground.

Transport for London has reported high levels of patronage, punctuality and customer satisfaction with its Overground services. Passenger numbers on the East London Line have doubled during its first year of operation, TfL claims.

Overground is at the top of Network Rail’s punctuality performance tables and an independent poll published at the end of June has Overground at 89% customer satisfaction - the national average is 84%.

The Overground system is a big improvement on services previously running on inner London main line networks.

Modern rolling stock and communications systems are tangible advances on their predecessors, but also importantly, greater frequency of services is up from four to eight trains an hour. This has moved Overground into the realm of what London Rail’s managing director Mike Brown has called a “turn up and go service” - a level of frequency that amounts to passengers being able to disregard timetables.

Network Rail’s new signalling systems are playing a major role in TfL’s Overground success. Given that two thirds of the UK’s freight traffic by volume travels through the North London Line section of the network shared with Overground (with four freight trains per hour in each direction between the West Coast Main Line and east coast ports), it is a success worth shouting about.

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