First stage of Chiltern tunnel drive completed

THE two Tunnel Boring Machines (TBM) excavating HS2’s longest tunnels have completed the first stage of their drive under the Chiltern Hills. Florence and Cecilia have reached the location of the first ventilation shaft at Chalfont St Peter having bored a combined total of over 3.6 miles since beginning their journeys at the south portal alongside the M25 at West Hyde last summer. The TBMs are working simultaneously to create the north and southbound tunnels, each crewed by a team of 17 staff working in shifts and supported by 100 people on the surface. The Chalfont St Peter shaft will be the first of five that will provide ventilation and emergency access to the 10 mile-long twin bores. It is 78 metres deep and, once completed, will be covered by a headhouse resembling local farm buildings to help it to blend into the local landscape.