Challenging Ground Conditions Shape Early Works on Lower Thames Crossing

Preparatory works on the Lower Thames Crossing are continuing, despite engineers identifying highly challenging ground conditions at the site ahead of full construction.

Keith Bowers, project director for tunnels and approaches on the £11bn scheme, has said significant groundwork is required before the main build can get underway. The National Highways-led project is designed to ease congestion at the Dartford Crossing by creating a new strategic route between the A2/M2 near Gravesend and the A13 and M25 in Essex, using twin tunnels beneath the River Thames.

Speaking at the New Civil Engineering Tunnelling Conference, Bowers said early assessments of the terrain were daunting. He explained that the ground is extremely difficult to access and traverse, presenting risks even to heavy machinery.

“The first reaction when we saw the conditions was pretty stark,” he said. “It’s difficult to walk across, challenging to drive across, and machinery can easily get bogged down. That’s driven a lot of work to develop practical engineering solutions.”

He added that the land take for the tunnelling works is far greater than the tunnel alignments themselves, with large areas required for supporting infrastructure such as tunnel segment factories, slurry treatment facilities and logistics compounds.

Enabling works are now underway on both sides of the river, including the construction of haul roads and site compounds. At the same time, environmental surveys, archaeological investigations and detailed site assessments are being carried out to inform the next phase of the project.

These early investigations have already revealed archaeological interest, including Roman pottery believed to have originated from mainland Europe. Bowers noted the area appears to have been used as a trading location during the Roman period.

The scheme received development consent in March, with full construction expected to begin in 2026. Once completed, the Lower Thames Crossing will be the longest road tunnel in the UK, with opening currently anticipated in the early 2030s.

Despite its role in the national road network, the project remains controversial. Critics continue to raise concerns over environmental impacts, air quality and the scale of construction traffic required during delivery.

In the most recent Budget, Chancellor Rachel Reeves allocated £891m to the scheme, describing it as part of the infrastructure underpinning long-term economic growth. However, figures released late last year suggest more than £3bn of the overall cost will ultimately be funded by taxpayers, despite plans to involve significant private investment.

Chris Todd, director of campaign group Transport Action Network, warned that escalating costs could undermine the project’s benefits. He said supporters risk being “short-changed” as budgets increase, adding that rising costs are likely to lead to higher tolls at both Dartford and the Lower Thames Crossing for many years.

The Department for Transport has reaffirmed its backing for the scheme. A spokesperson said ministers remain responsible for key decisions, while National Highways continues to oversee delivery.

The spokesperson added: “We have committed a further £891m to complete the publicly funded enabling works, allowing the private sector to move forward with construction and long-term operation of the crossing.”