By rosebell
Hochtief UK has completed one of the most technically challenging phases of National Grid’s Eryri Visual Impact Provision (VIP) project, with tunnel boring machine (TBM) Buddug breaking through beneath the Dwyryd Estuary.
Since tunnelling began in May 2025, the Herrenknecht TBM has excavated a 3.4km-long tunnel between Minffordd and Llandecwyn, reaching a 57m-deep reception shaft. The drive encountered challenging and varied geological conditions beneath the estuary.
Tunnel to accommodate 400kV electricity cables
The tunnel will house new 400kV electricity cables, replacing an existing section of overhead transmission line supported by 10 pylons crossing the landscape within Eryri National Park.
Once the new underground connection becomes operational, the existing overhead line and pylons will be removed, reducing the visual impact of electricity infrastructure in the protected landscape.
Eryri VIP project senior project manager Steve Ellison described the breakthrough as a significant achievement, highlighting the expertise, innovation and teamwork required to complete the estuary crossing.
He also thanked the delivery partners, tunnelling teams and local communities for supporting the construction phase.
Next phase focuses on cable installation
With excavation complete, work will move to removing TBM Buddug, installing the new electricity cables and completing the tunnel headhouses and associated infrastructure at both ends of the route.
The breakthrough was marked by events for project stakeholders, local school pupils and community members. Attendees had the opportunity to learn about the tunnelling operation and geology, view footage from inside the tunnel and celebrate the milestone.
The project will ultimately place the electricity connection underground, helping preserve the visual character of Eryri National Park.
