Highways England has opened discussions over building a new two-mile long tunnel at Gravesend, UK, for the first major Thames crossing in over 25 years to link Kent and Essex.
The discussions have seen the other option near the existing Dartford Crossing dropped in favour of the more eastern crossing point between Tilbury and Gravesend.
Studies by Highways England engineers showed that a bridge remains the cheapest option for the site at an estimated cost of up to £5.5 billion (€7.2 billion), while an immersed tunnel would be expected to top £6 billion (€7.89 billion).
But a bored tunnel is being favoured because it also offers the lowest environmental impact in the region, while estimated to cost anywhere between £4.3 billion (€5.6 billion) and £5.9 billion (€7.7 billion), including new motorway approach roads.
The new road would be 15 miles long with a dual carriageway width twin-bored tunnel. During development of the design, an additional lane in each direction of the tunnel will be considered to future-proof the crossing.
The proposed scheme would run from the end of the M2, crossing the river just east of Gravesend and Tilbury and joining the M25 between junctions 29 and 30.
Subject to the necessary funding and planning approvals, the new crossing would be open in 2025, if publicly funded. If private funding is also being used to meet the costs of the project, the crossing would open by 2027.
Highways England senior project manager, Martin Potts said, “By choosing a tunnel rather than a bridge we can minimise the effects of the new road on the environment.”