Hochtief UK has completed tunnelling beneath the Dwyryd Estuary in Wales – one of the most technically complex phases of National Grid’s Eryri Visual Impact Provision (VIP) project.
Since tunnelling began in May 2025, Herrenknecht TBM Buddug has excavated a 3.4km tunnel between Minffordd and Llandecwyn beneath the Dwyryd Estuary to arrive at the 57m-deep reception shaft. The drive under the estuary presented challenging and varied geology.
Once completed, the tunnel will house the new 400kV electricity cables that will replace the section of overhead line and 10 pylons that currently cross the landscape within the Eryri National Park.
Eryri VIP project senior project manager Steve Ellison TBM said Buddug’s breakthrough was “a fantastic achievement and a significant milestone for everyone involved”.
“Completing a 3.4km tunnel beneath the Dwyryd Estuary has required expertise, innovation and teamwork from a wide range of specialists,” he said.
“I would like to thank our delivery partners, the tunnelling teams and the local communities who have supported the project throughout this phase of construction. While tunnelling is now complete, there is still important work ahead as we prepare to install the new cables and continue construction of the tunnel headhouses.”
The TBM breakthrough was marked with a series of events for stakeholders, local school pupils and members of the community, providing an opportunity to learn more about the tunnelling operation, geology, view footage from inside the tunnel and celebrate the progress made on the project.
With tunnelling now complete, the project will move into its next construction phase. This includes removing the TBM, installing the new electricity cables in the tunnel and continuing the construction of infrastructure required at either end of the route.
Once the new connection is operational, the existing overhead line crossing the Dwyryd Estuary and its pylons will be removed, helping to reduce the visual impact of electricity infrastructure in the national park.
