A major consideration with any tunnel construction work is that it is often proposed based on the needs of the present but needs to be designed for the needs of the future.

This is not only to ensure that the infrastructure project is fit for purpose both on day one and far into the future, but also to be mindful of potential issues that could lead to delays.

This means that conveyor belt repair services, machine maintenance and the changing cost of parts and labour need to be factored into any proposal, and a certain tolerance needs to be applied to account for the realities of long-term construction.

This is part of the reason why a transatlantic tunnel is unlikely to ever happen; even if the materials and transportation solutions were practically possible, the time it would take would cause costs to increase exponentially due to the effects of inflation.

This makes the early opening of the Silvertown Tunnel on 7th April 2025 notable, even if the concept has been circulating for over three decades and loose proposals have been made since the 1960s.

Why Was The Silvertown Tunnel Needed?

Congestion is a frequent issue in London, and whilst many different proposals have been attempted to try and alleviate the issue, the Silvertown Tunnel is in some respects a mixture of a wide range of transport philosophies.

From the construction of the southbound bore of Blackwall Tunnel in 1967, there had been multiple proposals for a crossing east of Tower Bridge to fix the heavy congestion that London had already become infamous for.

The Blackwall Tunnel is regularly prone to closures due to its unusual size and shape for modern vehicles and the sheer number of vehicles that use it every day. At peak times, 3000 cars per hour drive through it.

Several proposals reached an advanced stage of planning but whilst they were not constructed they did guide the ultimate construction of the Silvertown Tunnel.

The first was the East London River Crossing, initially proposed in the 1970s which would have crossed the Thames from Gallions Reach to Falconwood, connecting the North Circular Road and A2 respectively.

This was abandoned in 1983, but it led to the development of the Thames Gateway Bridge proposal, which would have instead linked Gallions Reach to Thamesmead.

As part of this work, proposals for a crossing close to the existing Blackwall Tunnel led to the safeguarding of a potential Silvertown route from potential development conflicts.

Eventually, the proposed Gateway Bridge became a tunnel before it was cancelled in 2008, consulted on again in 2012 and finally approved in 2018.

How Did It Open Early Despite Being Behind Schedule? 

The construction contract was awarded in 2019, but construction did not begin until 2021, due to safety regulations concerning social distancing on construction projects.

The tunnel boring process began in late 2022, with the delay explained by Transport for London as being caused by inflation and shortages in materials, a byproduct of issues caused partly by a global pandemic and partly by the 2021 blockage of the Suez Canal which had reverberating effects on the supply chain.

This led in 2022 to a delay to the proposed April 2025 opening to the following month according to an article at the time by New Civil Engineer.

However, within a year when the TBM machine completed its work by September and the cut-and-cover and road realignment works were both progressing, it was reported in New Civil Engineer in early 2024 that the tunnel would be completed ahead of schedule.

In practice, the delay and the early completion cancelled each other out; the initial proposed opening date was in April 2025. This was delayed until May and then brought back forward to May.

Despite this, it is a remarkable achievement that highlights the variability of large-scale infrastructure projects and the importance of organisation.

Part of this involved factors far out of the control of the construction team; in 2022, material and energy costs were affected by a perfect storm of global factors that would inevitably start to ease up over the following years.

The completion of the major and most complicated pieces of work, namely the tunnel boring and construction of the precast concrete segments, also helped timescale considerations, and planning for variability allows for good news as well as bad.

Ultimately, the success of the Silvertown Tunnel is the success of contingency planning and hard work at every step of the construction process, one that may serve as a case study in the years to come.