Chesham Road intervention shaft
There will be four ventilation shafts and one intervention shaft in the tunnel across the Chilterns. These will also be used for emergency access during operation. The intervention shaft will be alongside the B485 Chesham Road in South Heath and just 1km from the north tunnel portal.
The shaft will not have ventilation fans nor a headhouse basement. It will be built using the caisson construction method. The site will also house an auto-transformer station. The shaft depth will be 43.5 metres and the tunnels will be 33 metres below ground. The tunnel boring machines will reach here in December 2023. The shaft is due to be completed by March 2025.
The approved access route is via the B485, A413, A355 to Beaconsfield then the A40 and the M40. Public Right of Way (PRoW) GMI 33/4 will be temporarily diverted before being reinstated along its original alignment.