Keltbray will provide construction services for the tunnel ventilation shafts in Amersham and Little Missenden. Excavation of the shaft in Amersham will be to a depth of 55m.
The contract extension follows Align JV bringing in Keltbray for the first two ventilation shafts and head houses at Chalfont St Peter and Chalfont St Giles. That first contract was awarded in August 2021. [See our previous report here.]
The shafts will provide ventilation and emergency access to the 10-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 Align joint venture – Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick – has a £1.6bn (Apr2020) contract to build the Chiltern tunnels and Colne Valley viaduct for the HS2 rail project.