Construction of two tunnels to take power into the Olympic Park has been completed, the Olympic Delivery Authority (ODA) announced yesterday.
Four Tunnel Boring Machines (TBMs) dug the two 6km long bores, and despite a delay to the breakthrough of the fourth and final TBM, the ODA claimed the £230M project had been completed on time and to budget. ODA chief executive David Higgins said, 'Burying the powerlines underground is essential in unlocking the Olympic Park site for the start of construction next year and is a vital part of the long term regeneration of east London.'The successful completion of this massive tunnelling project on time and on budget gives us real momentum as we set our sights on the challenge ahead.'Delays to the final TBM breakthrough were caused by difficulties in de-watering a 10m diameter, 26m deep shaft which will be used to connect power cables into an electricity substation in Hackney.Contractor Murphy built a secant piled wall around the shaft to prevent water flooding the tunnel (NCE 19 April 2007).The overall project was kept on track by mechanical and electrical contractors working in completed sections of the tunnel before the final breakthrough.Two 4.15m diameter TBMs moving in opposite directions underneath Stratford, east London bored the tunnel to take National Grid power lines underground. Two other 2.82m diameter TBMs did the same on a second tunnel for EDF Energy power lines.This will allow 52 electricity pylons to be demolished so that construction work on the Olympic park can start next summer.