A seven-year project for the National Grid to rewire London via deep underground tunnels.

Record-breaking tunnelling contract

Working together in a joint venture, Skanska and Costain (CSJV) completed a new electricity superhighway far below the capital – the longest ever single tunnelling contract awarded in London.

The project was designed to meet increasing demand and help keep Londoners connected to safe and reliable electricity supplies.

Constructing access tunnels

The CSJV built around 32km of a high voltage electricity cable tunnel that runs between Hackney and Willesden (via Kensal Green) Kensal Green and Wimbledon.

The work included construction of 14 access shafts (up to 40m deep and mainly between 12m and 15m in diameter), associated head houses, culverts, mechanical and electrical systems, tunnel ventilation, communications and headhouse building services.

The CSJV managed and co-ordinated the works with other principal contractors, including two main cable contractors, six substation contractors, an over-site residential developer at Earls Court and a third-party substation developer.