Keltbray has secured a £12 million extension to its current C1 Shaft contract to provide construction services for the next two ventilation shafts along HS2's two giant tunnel drives through the Chiltern Hills, on behalf of the Align Joint Venture that is delivering the Central 1 (C1) portion of HS2 Phase 1. The announcement comes following the news that Keltbray secured the contract for first two ventilation shafts on the project in August earlier this year.


The next two shafts on the contract are located at Amersham and Little Missenden. Excavation of the shaft in Amersham will be to a depth of 55m.

The shafts will provide ventilation and emergency access to the ten-mile long tunnels Align is digging under the Chiltern Hills. The full scope of services Keltbray will provide include:

• Reinforced concrete works at the base of the shafts, to create a collar structure to enable the TBMs to pass through the base of the shaft

• Internal shaft construction works to build slip-formed concrete cores and lining walls

• Excavation and substructure construction of Head House buildings.

The tunnels form part of the HS2 network that will help connect the country, create thousands of jobs and rebalance the UK economy.