River Medway Cable Tunnels

[2] Grain sealing end compound location: 51°26'09.4"N 0°42'18.9"E Chetney Marsh sealing end compound location: 51°25'14.6"N 0°41'59.6"E The tunnels were built in anticipation of the commissioning of Grain power station (with a planned capacity of 3,300 MW).

Overhead lines would have been longer than the 1,382 metre Swanscombe to Thurrock 400kV crossing and therefore require taller pylons.

[2] The tunnels were designed by the Transmission Development and Construction Division of the Central Electricity Generating Board advised by Charles Haswell and Partners.

Unexpected beds of gravel and silt were encountered and entailed a diversion of the west tunnel.

[2] The cables are air cooled to maintain the temperature within design limits at high electricity loads.