Severn-Wye Cable Tunnel

The Severn-Wye Cable Tunnel, also known as the Severn Cable Tunnel, carries high-voltage (400 kV) electricity transmission lines beneath the estuaries of the River Severn and River Wye between Newhouse (Mathern), Monmouthshire and Aust, South Gloucestershire.

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Tunnel data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).

Other tunnels in United Kingdom

Delaware Aqueduct United States · 137 km Päijänne Water Tunnel Finland · 120 km Orange–Fish River Tunnel South Africa · 82.8 km Ishikawa Tunnel Japan · 78.5 km Brenner Base Tunnel Austria · 64 km Mont d'Ambin base tunnel France · 57.5 km Gotthard Base Tunnel Switzerland · 57.09 km Hong Kong–Zhuhai–Macau Bridge China · 55 km