2012 Olympic Games Powerline Tunnel Breaks Through in LondonTunnelling work took a significant step forward with a scheduled breakthrough in one of the two tunnels being built to underground the powerlines in the Olympic Park site in East London in preparation for the London 2012 Olympic Games and Paralympic Games. The Lovat TBM named 'Fionnuala' broke through into the deep shaft at Quartermile Lane exactly on schedule. The breakthrough means that tunnelling is on track and the halfway point in the first tunnel has now been passed. There is still a lot of work to come, but the project is now over a third of the way towards completing the tunnelling distance needed. 4.6 km of tunnelling out of a combined total distance of 13 km has now been completed. The powerlines which currently overshadow the Olympic Park area in the Lower Lea Valley are to be placed in two tunnels underground, with 52 electricity pylons demolished along the six kilometre route from Hackney to West Ham enabling construction on site. The underground powerlines will connect Hackney and West Ham substation, part of the grid that supplies London from Holloway in the north, The City in the west and Docklands in the south. They will travel west of the Stratford City development site and beneath Hackney Marshes. The two tunnels (each 6 km long with an additional 1 km spur tunnel) are between 3 m to 4.5 m in diameter, both requiring sophisticated ventilation, and lined with 11,000 concrete rings fitted with gaskets to ensure they are watertight.Lovat has provided J. Murphy & Sons with engineering, components and technical support for the modifications and refurbishment of two TBMs prior to launch. The TBMs are driving through saturated Thanet sands and Lambeth beds. 'Fionnuala' was lowered into the shaft on 3rd July, 2006 and started mining on 14th July. It has reported a best shift: 21 rings (10 hours), best day: 41 rings (20 hours), and best week: 168 rings (5 days). The other TBM, dubbed 'Helen', was lowered into the shaft at 14th June, 2006 and started mining on 23rd June. It has reported a best shift: 16 rings (10 hours), best day: 30 rings (20 hours), and best week: 151 rings (5 days). Visit www.lovat.com Over 350 people are currently working on the site with four tunnelling machines working 25 m below ground. Work takes place 24 hours a day, seven days a week on what is the largest tunnel project in the country. 250,000 cubic metres of spoil will be produced by the tunnelling, which will be then be re-used to construct the Olympic Park.The project is scheduled for completion in 2009 when power will be switched from overhead to the underground supply. When the tunnelling is complete, 200 km of cables will be installed by EDF Energy and National Grid working with the Olympic Delivery Authority. The overall project budget for undergrounding of powerlines is around GBP230 million funded by the government for the long-term regeneration of the Lower Lea Valley. Click here and uk/28. 49/06.