Going Underground

Lea Valley Cable Tunnels

At first sight, a project that involves rerouting power lines may seem insignificant or even described as a bit boring. However, the complex and challenging project to move two sets of existing power lines from pylons into tunnels was fundamental to the Olympic Park site. Without the removal of these power lines that went through the centre of the planned Olympic park the development of the rest of the venues could literally not get off the ground.



The bare bones of the project included the creation of 10 shafts, 13 km of tunnels, over 200km of cabling and the removal of 52 existing overhead pylons adding up to a project cost of £250 million. Significant hurdles had to be overcome from the outset: difficult ground conditions, approval from a plethora of landowners, river crossings and utility approvals, and a very challenging deadline of three and a half years (half the industry norm). Extensive offsite trials were conducted in tunnel mock-up environments to develop both cable installation and jointing techniques.

The tunnelling and shaft work were completed by August 2007 – 13km in 13 months. Laying of the cables proved to be just as challenging. the innovative design of cable rollers and use of bespoke tunnel vehicles for plant and materials transportation allowed up to three cable lengths totalling 2400m to be pulled through the tunnel at any one time. Cable lengths for the 400 kV cables were such that the joint bays were spaced at 800m centres. Hundreds of metres of galvanized cable support systems have been used throughout the tunnels to ensure that no costly maintenance is needed for these systems.

The power was switched underground during August 2008, allowing work to remove the overhead pylons and overhead lines to begin in September 2008. The careful planning, collaboration and innovation used by the project team set a benchmark for world-class delivery of high-voltage cable tunnels.

Image: London 2012

Posted on June 15, 2012 by untitled

Read next…

Galvanizing Delight

Studio East Dining was a temporary pavilion, designed by Carmody Groarke, built on top of an eight-storey car park adjacent to the Olympic site. The structure was made entirely out of standard galvanized scaffolding poles taken from the site and…

Read more

London Olympics 2012

When, in July 2005, the IOC president Jacques Rogge made the dramatic announcement that London had won the campaign to host the 2012 Olympics, it set off a dramatic programme of planning, building and organising that may well go on…

Read more

London Velodrome

Bikes ridden at speed around a banked arena seem to draw upon some primeval instinct that engenders a competitive edge for the riders and an almost uncontrollable zeal amongst the watching crowd. Maybe there is an intrinsic link within the…

Read more

Olympic Park

Situated to the east of London, encompassing four of the most deprived boroughs of London, the site that has become the Olympic Park started from very humble beginnings. The full legacy of centuries of industrial activity on the site became…

Read more