
Chalfont St Giles vent shaft
There will be four ventilation shafts and one intervention shaft in the tunnel across the Chilterns. These would also be used for emergency access during operation. All the ventilation shafts use the same diaphragm wall construction method. The second of these will be in Bottom House Farm Lane, Chalfont St Giles which will be closed to through traffic for approximately two years. The shaft depth here is 32 metres. The tunnel boring machines will reach here in August 2022. The vent shaft is due to be completed by January 2025. The site will also house an auto-transformer station. To protect water supplies a pipeline has been built between the Affinity Water pumping stations at Chalfont St Giles and Amersham. The approved access route is via a temporary haul road to the A413 then to the A40 and the M40. All HGVs will turn right when leaving the haul road. The junction will be controlled by temporary traffic lights.