Project Spotlight: Silvertown Tunnel

UK

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Silvertown Tunnel is a 1.4km twin-bored road tunnel project under the River Thames in East London, connecting the Greenwich Peninsula and West Silvertown. It aims to address the traffic congestion at Blackwall Tunnel and improve public transport links such as cross-river bus journeys.

The project commenced in 2019 and was initially projected to be operational by 2023. However, it has been postponed to September 2025 due to a combination of cost reassessment, construction challenges, complex operational planning, and efforts to mitigate the impact of these delays.

This tunnel project is necessary to alleviate traffic congestion on existing routes, specifically for the Blackwall Tunnel. The Blackwall Tunnel is also located under the River Thames in London but has limited capacity and cannot meet the increasing traffic volume.

Funding for the Silvertown Tunnel project

The funding for this project is approximately £1 billion and is managed through a design, build, finance, and maintain contract model supported by Transport for London (TfL). It is currently being carried out by the Riverlinx consortium, which involves Ferrovial Construction, BAM Nuttall, and SK E&C.

Balfour Beatty was selected as the construction advisor, and Atkins was selected to provide the reference design for the Silvertown Tunnel to serve as a basis for the Environmental Impact Assessment (EIA). Yee Associates partnered with Atkins to develop the architectural design for the tunnel.

The Silvertown Tunnel project is a critical infrastructure development in London’s transportation sector and will provide long-term benefits once it completes construction in September 2025.

How TBMs will be used to construct the Silvertown Tunnel?

The Silvertown Tunnel project involves constructing a new twin-bored tunnel under the River Thames, a task well-suited to the capabilities of a TBM. A twin-bore tunnel consists of two parallel tunnels, typically used to handle different directions of traffic. The use of this technology in the Silvertown Tunnel allows for precise and efficient excavation under the riverbed, ensuring minimal impact on the river ecosystem and surrounding areas.

A Tunnel Boring Machine (TBM) is an advanced mechanical system used to construct tunnels in various geological conditions. The cutter head is at the forefront of a TBM, a rotating face equipped with multiple cutting tools designed to grind through soil and rock. The machine has support mechanisms, including a shield for tunnel stabilisation, systems for removing excavated materials, and equipment for installing tunnel linings.  

TBMs significantly minimise surface disruption, thereby reducing the environmental impact of construction projects. They also improve worker safety and make tunnelling faster and safer than traditional methods like manual excavation or explosives. 

Tunnel Boring Machine ‘Jill’

Tunnel Boring Machine ‘Jill’ was used for the main tunnelling works of the Silvertown Tunnel project. It was specifically manufactured for the project and is the largest TBM by diameter in UK’s history.

Its impressive specifications include a cutter-face or shield diameter of 11.91 metres, approximately the width of three double-decker buses. When fully assembled, it spans a length of 82 metres and weighs 1800 tonnes. The TBM averaged about 22 meters per day during its journey under the river from Newham to Greenwich.

As all main tunnelling work was completed, ‘Jill’ was disassembled in Newham and recycled, ready for use by the manufacturer in future tunnelling projects.

Silvertown Tunnel design features  

Designed as a twin-bore tunnel, the tunnel connects the A1020 Silvertown Way/Lower Lea Crossing on the north side with the Blackwall Tunnel Approach on the south side. Each of the two tunnels will consist of two lanes with an internal width of 10.66 metres.

Emergency evacuation paths will also be included. This will handle significant traffic volume and accommodate buses and heavy goods vehicles. Moreover, all future bus routes using the tunnel will have zero emissions, aligning with the project’s environmental sustainability goals.

Access ramps that span 600 metres are also designed for modern transportation. Maintenance of buildings and sections of roads, such as a highway bridge and a footbridge for pedestrians, will also be key features of the Silvertown Tunnel project.

Environmental considerations of the Silvertown Tunnel project

The project integrates numerous sustainable considerations with a focus on reducing carbon emissions. The construction team for the Riverlinx consortium also focused on minimising local road congestion by transporting most construction materials via the river. This removes thousands of lorries from local roads and lowers carbon emissions. Riverlinx has reused excavated materials and concrete from demolitions, with all suitable materials being removed by barges.

In terms of design, Silvertown Tunnel incorporated the use of ramix® 4D 80/60BGP fibres in the tunnel lining under the River Thames. This eliminated the need for steel cages and thereby reduced carbon emissions.

Without the Silvertown Tunnel, the growing population of London will exacerbate congestion and deteriorate air quality around the Blackwall Tunnel.

Why is the Silvertown Tunnel required?

The Silvertown Tunnel addresses the growing traffic congestion and deteriorating air quality in East London, especially near the Blackwall Tunnel. With London’s increasing population, the existing infrastructure struggles to cope with the increasing traffic volume, causing regular delays and increased pollution. Adding another crossing under the Thames will alleviate these pressing issues. 

Constructing the tunnel will offer an alternative route, significantly reducing traffic congestion on existing tunnels and bridges. This reduces queues at the Blackwall Tunnel, with journeys taking up to 20 minutes faster. Congestion has always been a concern in London, so the project will help lower the number of times vehicles spend waiting in traffic.

The construction and operation of the Silvertown Tunnel are expected to boost the local economy. Support will be given to businesses in the catchment area after the tunnel opens, and it is estimated to create 286,000 jobs by 2036. This includes engineering, construction, retail, hospitality, healthcare, and several more fields.

After the tunnel is completed, it will improve accessibility between different parts of London, making it easier for people to access jobs, services, and amenities. More importantly, it ensures that emergency and essential services can move across the city more efficiently. This enhanced connectivity helps operational efficiency in urban areas like London.

The project is expected to improve air quality by significantly reducing carbon emissions. As there will be less congestion, it leads to a reduction in harmful emissions such as nitrogen oxides and particulates. Also, the dedicated bus lanes encourage the shift from private vehicles to public transport.

Challenges around the Silvertown Tunnel project

The Silvertown Tunnel project’s challenges and controversy are primarily centred around environmental concerns and its impact on local communities.

The tunnel’s construction and operation are expected to affect local communities, particularly in areas like Newham significantly. The influx of cars and heavy goods vehicles attracted to the tunnel may threaten air quality, exacerbating respiratory diseases caused by vehicle pollution. This is particularly concerning for areas in London that have already declared a climate emergency and are grappling with the health impacts of pollution. 

Silvertown Tunnel completed works and project status

In July 2023, the Silvertown Tunnel project achieved significant progress with TBM Jill, completing all main tunnelling work on the new river crossing in under a year.

Over 780,000 tonnes of spoil were removed by barge, and substantial development on the tunnel portal buildings continued on both sides of the Thames.

A new walking and cycling bridge over the A102 was also installed and opened, enhancing pedestrian and cyclist accessibility.

The Riverlinx consortium construction crew is currently excavating the eight cross-passages. Crews are also developing a new road layout leading into the Tidal Basin roundabout in Newham and connecting roads into the A2 south of the Blackwall Tunnel. 

Transport for London is coordinating with local communities and stakeholders to outline Silvertown Tunnel’s next step, including land acquisitions, construction logistics, and access requirements for residents and businesses.

The Silvertown Tunnel project is a key infrastructural development in London, poised to alleviate congestion and improve connectivity. Despite its challenges, the project’s progress of major tunnelling work and construction of access routes is set to enhance urban mobility and contribute to UK’s economic and environmental goals.

Image Sources: Copyright TfL

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