Preparatory work for the Lower Thames Crossing—the future title-holder of Europe’s largest road tunnel—is slated to begin in late 2025
Project Overview
Tunnel length: 2.6 miles (approx. 4.2 km) beneath the Thames.
Budget: Estimated between £9 billion and £10 billion
Opening target: Around 2032
This ambitious tunnel, backed by National Highways, is designed to relieve chronic congestion at the existing Dartford Crossing—the only road tunnel east of London. Once completed, it will become the widest and longest road tunnel in the UK, carrying three lanes each way in twin bores
Key Timeline and Milestones
March 25, 2025: Development consent officially granted
Late 2025: Enabling works, including soil treatment, begin at the northern tunnel portal
Autumn 2026: Construction of the tunnel-boring machine (TBM) launch shaft is expected to commence
Spring 2028: The TBM will begin its journey—boring through challenging soils before reaching chalk strata
2032: Tunnel set to open to traffic
Engineering & Geology Challenges
- The tunnel cuts through complex ground conditions:
- Initial sections consist of landfill, including waste and historical tunnelling debris, as well as peat, silt, and clay layers.
- Beneath these lies chalk, which is better for tunnelling. However, the first ~300 meters of boring will face highly unstable soils
- Alan Price of the Bouygues-Murphy JV described the terrain as "probably the worst geology anyone can find in England"
- Because of these conditions, extensive soil stabilization is required at the northern portal before boring can begin
Construction Details
Single TBM strategy: One massive machine—approximately 16.4 m in diameter—will bore one tunnel, be reversed, and used to bore the second. This saves costs and carbon emissions, though it extends the build time
The tunnel will feature 26 cross-passages between the twin bores
Environmental Considerations
- Opponents highlight possible impacts to ancient woodland, veteran trees, and wildlife habitats near the portals.
- In response, National Highways plans to plant over 260 hectares of woodland, create new habitats, and build seven wildlife bridges
- The project aims to be “Britain’s greenest road,” with six times more green space than road surface
In summary: The Lower Thames Crossing is set to revolutionize east Thames transport with a record-breaking, tri-lane road tunnel. Despite facing complex geology, a hefty price tag, and environmental scrutiny, construction is on track to start by the end of 2025, with the goal of relieving congestion and boosting connectivity by 2032. For further information please use the tunnelbuilder archive uk/91. 28/25.
