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Wednesday, May 22, 2024

Whitechapel – An Overground station going Underground

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The clock is ticking as the biggest, and one of the most complex, railway engineering projects in Europe moves into its final stages. Eventually, even the name will change, from the project title of Crossrail into the operational route’s Elizabeth line.

As the line’s new stations continue to emerge from below the ground, there is more and more visible evidence of this £14 billion scheme throughout the London conurbation. Additionally, after months of testing on the Liverpool Street to Shenfield railway line, Transport for London introduced the first of the brand new Class 345 trains in June this year, equipped with Wi-Fi and a solid 4G connection.

However, if we thought that most of the challenging engineering was now behind us, we would be far from the truth and a recent visit to Whitechapel Station to meet Crossrail’s project manager Kevin Brown confirmed this.

Important interchange

Whitechapel station is an important interchange for both the Hammersmith & City and District lines with London Overground. This site is proving to be one of the most challenging and congested, with the existing station’s protected Victorian facade, local community, school and The Royal London Hospital all closely snuggling up to the new station area.

Work started at Whitechapel back in December 2011, when three contracts were awarded for sinking shafts, digging tunnels and spraying concrete, for building a new underground station for Crossrail and for completely refurbishing the existing Overground and Underground stations.

The principal contractor for the main works at Whitechapel is BBMV, which is a joint venture encompassing Balfour Beatty, Morgan Sindall and Vinci Construction. The concept design was developed by Arcadis and BDP Architects, then consultant Baker Hicks worked alongside BBMV to develop detailed designs for use by the joint venture and its supply chain.

The planned completion date for all the work is the summer of 2018, when it will form part of the new route ready for final testing before going live in December 2018.

Elevated station concourse

The design adopted includes the construction of a new Elizabeth line station that will weave between the existing transport services onto an elevated station concourse, which is designed to act as a bridge for passengers and the local community. The new station platforms will be 32 metres below ground.

Access to all interchange services will be from a spacious new ticket hall sitting on a bridge above the Victorian railway. Entry to the station will be through the refurbished original entrance on Whitechapel Road but, in the interim, the existing station entrance has been closed and a temporary ticket hall and control centre constructed. To improve connectivity to the surrounding area, a new second entrance will be provided on Durward Street at the northern end of the concourse.

The new station concourse will rise from Whitechapel Road over the East-West Underground lines and above the North-South Overground lines before dipping under the road bridge at Durward Street. It continues along the course of the railway cutting where it then allows access to the new platforms.

The raised concourse structure will be supported by steel struts, resting partially on the brick retaining walls of the Overground cutting. The concept is for the concourse to appear to be floating in the space, allowing daylight to stream down on to the Overground platforms.

Environmental benefits

The concourse will be covered by a ‘green roof’, topped with sedum plants, and will dip down under the new Durward Street bridge. The intention is that this design will also provide several other environmental benefits including improvements to air quality, noise and storm water attenuation, conservation and biodiversity. The natural light and fresh air from the station concourse will certainly help to create a calm, open, brightly-lit environment, an ambience that will be welcome in this busy congested part of the capital.

A new square at the northern side of the station will provide a public space with raised lawns and cycle parking. Three escalators and a lift shaft will give access to the Elizabeth line platform at the northern end. The existing Victorian station frontage on Whitechapel Road, built in 1867, will be refurbished. Also, there will be a widened stone-paved footway which will form a forecourt for the new ticket hall and concourse. A pedestrian crossing, providing safe passage to the Royal London Hospital, will be reinstated at this point.

Finally, to the west, Court Street, leading to a pedestrian bridge over the Underground tracks, will be made vehicle-free, with improved paving and lighting.

The Crossrail project as a whole is now 85 per cent complete. At the tightly constrained, busy, urban location of Whitechapel station, that figure is around 80 per cent.

Two major shafts

A significant amount of piling work has been carried out by BBMV, supported by Bachy Soletanche and Balfour Beatty Ground Engineering. Alongside the piling work, two shafts have been constructed by an earlier contract under a BAM Nuttall/Kier JV. To the east of the site is the Cambridge Heath Shaft, which has been designed to accommodate a ticket hall connection although, at present, it is primarily for ventilation and emergency access.

The second is the Durward Street Shaft. This is in the centre of the site and is designed to house the ventilation and railway systems, three escalator shafts and a lift shaft.

Alongside, a significant amount of tunnelling work has been carried out. In total, Kevin Brown estimates that more than 1,000 metres of tunnel has been excavated to form cross passages, escalator shafts, new station platforms and an open area to the west of the new platforms to accommodate a track crossover. As this work progressed, the new tunnel linings were reinforced and lined with sprayed concrete.

Arrival of the TBM

On the 4 April 2014, the 150-metre long, 1,000-tonne tunnel boring machine (TBM) Elizabeth, working from Limmo Peninsula in East London, broke into the huge space of the Westbound platform tunnel. It then travelled slowly through the 325 metres of the mined tunnel section to the west end, where it broke out through the sprayed concrete wall and carried on creating the 7.1-metre-diameter tunnels, working towards Liverpool Street. This was subsequently followed by a second TBM, Victoria, boring the eastbound tunnel.

By winter 2015, the first key milestone had been reached. The construction of Whitechapel’s temporary ticket hall and control centre was complete and they were handed over to London Underground. This interim station is designed to re-route passengers out of the station, away from all the engineering works that could now take place in a safe environment with minimal disruption to the existing Underground and Overground services.

This significant project milestone meant that all the technical systems involved in running the station complex could now be migrated from the original main station building while it is upgraded, to make way for the new concourse.

An uphill excavator

The team had planned to excavate the escalator shaft tunnel at the same time as excavating the Durward Street shaft. There was a conflict of movement between the two activities which meant that, to avoid any delays, the diagonally poised tunnels had to be dug from the bottom to the top. This was not an easy task, and it called for some inspirational engineering.

The solution was an ‘Uphill Excavator’, suspended from the roof of the tunnel (above). In this position, the excavator could travel up the designed gradient, scoop up the earth as it went and pass it back down underneath the machine to be carted away. The innovative idea worked, it kept the project on schedule and won an award for innovation.

Kevin pointed out the importance of teamwork and good relationships to the project’s success. Both London Underground and Overground teams work closely with the Crossrail project team. Kevin is clear that, without this approach, the project would be impossible to complete. In addition, one of the clear outcomes from this collaborative working is that there have been no unplanned delays to trains resulting from this work.

Silence during the exam

It is a similar experience with the local community. Whilst school exams were in progress, noise and disruption were kept to a minimum and, in return, during the summer holidays, the team have been given access to the school area, providing invaluable additional storage space for materials and equipment and better access to the site.

The project has also provided employment opportunities, and many of the young engineers have impressed Kevin and the senior members of the team with their commitment and often-innovative thinking.

The emphasis on pre-fabricating structural units off-site to minimise construction time, as well as risk and hazards on site, is evident in the final stages of the work as the platforms start to take shape and the new station areas are equipped with escalators and lifts.

Safety record

While work was underway in 2015, the team recorded one million working hours without a RIDDOR (Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 2013) incident. This finally rose to pass 3.5 million working hours, an excellent achievement by anyone’s standards given that work is taking place around the clock and in a 24hr cycle where there are about 800 workers on site in a very challenging environment.

It is estimated that more than 13 million passengers will use the Whitechapel Elizabeth line station each year and, at peak times, there will be 24 trains per hour stopping at Whitechapel in each direction. Journey times to Heathrow will take about 40 minutes. The Victorian face of the station will be cleaned and unchanged.

With the remaining 20 per cent of the programme, which will see the fitting out of the new station and all that entails, well underway, a bright new Elizabeth line station with plenty of breathing space will be ready to address the demands of the twenty-first century travelling public from December 2018.

Written by Collin Carr

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