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.