Hochtief to build National Grid’s Snowdonia tunnel

The project is part of the Visual Impact Provision project in the Snowdonia National Park and involves removing 10 pylons and 3km of overhead power lines, running from Minffordd, across the Dwyryd Estuary, and eastwards to just beyond Cilfor, and putting them in a tunnel.

The seven-year project will require the construction of two shafts and a 3.4km tunnel to carry electricity under the Dwyryd Estuary. National Grid will start environmental and archaeological survey works in the coming months and the construction sites at Garth and Cilfor will be established in the autumn. The programme of shaft sinking, tunnel construction, head house construction, cable installation and commissioning will commence in 2023 and pylon removal is expected in 2029.

The project has been developed to reduce the visual impact of National Grid’s overhead line across the estuary.

It is Hochtief’s second tunnelling project for National Grid. The Hochtief Murphy joint venture is delivering 32km of tunnels for the supply of electricity in London. The £400m (US$554m) second phase (LPT2) of National Grid’s £1bn (US$1.38bn) London Power Tunnels project is due for completion in 2026.

In Sweden, the Hochtief Implenia JV is currently building a 14km power supply tunnel below the city of Stockholm. The Anneberg-Skanstull Tunnel has a 5m diameter and lies 50-100m below ground. The project also includes six ventilation shafts, elevators, and the construction of technical buildings for electrotechnical equipment. Scheduled for completion in 2024, it is part of the City Link project intended to improve electricity supply in the greater Stockholm area.