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. The first of these will be in Chesham Lane, Chalfont St Peter. The construction compound will be in place for seven years. Shaft depth is 63 metres. Tunnel boring machines will reach here in September 2021. The access route to the compound will be via a newly constructed temporary haul road directly to the A413 then to the A40 and the M40. All HGVs will turn left when leaving the haul road. Junction will be controlled by temporary traffic lights.
PRoW (Public Right of Way) CSP10 will be diverted east around the construction compound before joining the existing footpath CSP 9 south of The Brow for the duration of construction and then reinstated along its original alignment.