An underground view of the London 2012 power tunnels.; An underground view of the London 2012 power tunnels.;

London 2012 Powerlines Undergrounding, London

Relocating powerlines to unlock Olympic Park landscape for London 2012

The Powerlines Undergrounding (PLUG) project was fundamental to unlocking the Olympic Park site for the London 2012 Olympic and Paralympic Games, and the long-term regeneration of the Lower Lea Valley area of East London. It was one of the most complex engineering and tunnelling projects in Europe at the time.

The £250m project involved fast-tracking the plan to relocate 52 electricity pylons that dominated the landscape in and around the Olympic Park site, to clear the area ready for construction.

Arup’s role included the project management of the £130m design and build IChemE target cost contract for the tunnel works. The tight programme required constant re-focusing of the team’s efforts onto the critical activities and detailed coordination of construction methodologies and programmes.

Arup created two 6km long deep bored tunnels (typically 20-30m below ground) and an 850m long spur tunnel to carry the powerlines underneath the Olympic Park, together with associated substation works.

Four tunnel boring machines worked simultaneously, with 420 workers on site and 200km of power cables – enough to stretch from London to Nottingham.

On completion the tunnels, power cables and substations would form part of the strategic infrastructure of UK Power Networks and National Grid. Therefore, Arup’s role involved extensive coordination of multiple stakeholder groups, including numerous technical approvals from third parties – 20 rail, six river and over 60 utilities.

PLUG was the first major construction project for the Olympics and, as part of its commitment to transparency, the Olympic Delivery Authority (ODA) published a detailed set of milestones at the outset. Conducted in the public realm, any deviation from the original timetable had the potential to dent public confidence.

'Helen' – one of the tunnel boring machines used on the project.

Risk management

The project was delivered against a challenging deadline of 3.5 years, half the industry norm, within budget. The successful outcome was aided by a risk management process, which was developed by Arup and cited as best practice by the ODA. Amongst other contributions, it highlighted the risk of short-notice cancellation of outage windows and prompted the development of cost-effective contingency plans.

Careful planning, collaborative working and innovation used by the project team set a benchmark for delivery of high-voltage cable tunnels, winning the Association for Project Management’s Project of the Year Award in 2009.


The project was sustainable from the outset. 90% of the 175,000m³ of the spoil produced has been re-used in the earthworks for the Olympic Park. Many of the removed parts then went on to be recycled including 52 electricity transmission pylons, 80km of conductors and 8 tonnes of porcelain insulators.