River Medway Cable Tunnels
The River Medway Cable Tunnels are a pair of tunnels carrying high-voltage electricity transmission lines beneath the lower River Medway between the Isle of Grain and Chetney Marshes, Kent. == Specification == Each tunnel carries a 400 kV electricity circuit on the transmission line between the National Grid substations at Grain and Kemsley (Line Reference: 4TL).
Source: Wikipedia — River Medway Cable Tunnels (CC BY-SA 4.0)