Complex ground conditions emerge as £11bn Lower Thames Crossing preparation work continues

Preparatory construction works on the Lower Thames Crossing are progressing, despite early assessments identifying difficult ground conditions at the site.

Keith Bowers, project director for tunnels and approaches on the Lower Thames Crossing, has acknowledged that extensive groundwork is required before main construction can begin. The £11bn project, led by National Highways, is intended to reduce pressure on the Dartford Crossing by creating a new route linking the A2/M2 near Gravesend with the A13 and M25 in Essex via two tunnels beneath the River Thames.

Speaking at the New Civil Engineering Tunnelling conference, Mr Bowers described the challenges presented by the site’s terrain. He said: “I think a lot of people’s first reactions the first time we saw the ground conditions out there was ‘help!’ – this is not really where you want to be doing anything much.

“It’s quite difficult to walk across; it’s a bit of an operation to drive a Land Rover across it.

“You can lose machines in there and all sorts. It’s generally quite challenging. There’s a lot of work going on developing the solutions for that.”

He explained that the land required for the tunnelling operation extends well beyond the tunnel footprints themselves, as additional space is needed for supporting infrastructure such as segment manufacturing facilities and slurry treatment plants.

Enabling works are currently taking place on both sides of the Thames, with activities including the formation of haul roads and the establishment of site compounds. Alongside this, teams are carrying out ecological and archaeological investigations, as well as detailed surveys to inform later construction stages.

During these investigations, the team has uncovered “quite fine Roman pottery from Europe”, with Mr Bowers noting that the location was previously used by the Romans as a “trading location”.

The project received development consent from the government in March, and full construction is now anticipated to start in 2026. Once operational, the Lower Thames Crossing is expected to become the longest road tunnel in the UK, with completion currently forecast for the early 2030s.

Despite its strategic importance, the scheme continues to attract criticism, particularly around environmental impact, air quality concerns and the volume of construction traffic expected during delivery.

In the recent Budget, Chancellor Rachel Reeves committed £891m towards the project, describing it as part of the infrastructure that forms the “backbone of economic growth across our country”. However, figures published in November indicated that more than £3bn of the overall cost will still be met by taxpayers, despite plans to rely heavily on private finance.

Chris Todd, director of the Transport Action Network and a vocal opponent of the project, warned that supporters of the scheme could be left disappointed as costs continue to rise. He said those “cheering on” the crossing would ultimately be “short-changed, as costs have predictably ballooned”.

He added: “This will result in higher tolls at Dartford and LTC for decades to come, much as we have previously predicted.”

A spokesperson for the Department for Transport reiterated the government’s commitment to the project, saying: “We are backing the Lower Thames Crossing project, and while ministers are responsible for key decisions, National Highways continues to lead its delivery.

“We have committed a further £891m to complete the publicly funded works to enable the private sector to take forward its construction and long-term operation.”