Chalfont St Giles vent shaft

There are four ventilation shafts and one intervention shaft in the tunnel across the Chilterns. These would also be used for emergency access during operation. The second of these will be in Bottom House Farm Lane, Chalfont St Giles. A temporary haul road links the shaft site to the A413.

All the ventilation shafts used the same diaphragm wall construction method. Ventilation fans will be housed in a basement below a single storey headhouse. The shaft depth here is 32 metres and the tunnels are 26 metres below ground. The vent shaft is due to be completed by January 2025. The site will also house an auto-transformer station. The tunnel boring machines reached here in September 2022. North of the vent shaft the tunnels pass 90 metres below the A355 Gore Hill and then on towards the Amersham vent shaft.

To protect water supplies a pipeline was 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.

Chalfont St Giles vent shaft looking north – May 2016 (04_555)
Chalfont St Giles vent shaft looking north – Oct. 2022 (04_559)
Chalfont St Giles vent shaft – Apr. 2024 (04_597)
Looking across the basement towards the top of the shaft – Apr. 2024 (04_586)
Basement looking towards the top of the shaft – Apr. 2024 (04_585)
Looking across the base of the shaft towards the ‘down’ tunnel – Apr. 2024 (04_584)
Chalfont St Giles vent shaft looking west – Jan. 2024 (04_583)
Chalfont St Giles vent shaft – Jan. 2024 (04_582)
Chalfont St Giles vent shaft headhouse – Jan. 2024 (04_581)
Adit leading to down tunnel the down tunnel – Jan. 2024 (04_580)
Down tunnel looking north towards the shaft connection – Jan. 2024 (04_579)
The basement looking towards the shaft – Jan. 2024 (04_578)
Vent outlet – Jan. 2024 (04_577)
Vent outlet building – Jan. 2024 (04_576)
Auto transformer station base – Jan, 2024 (04_575)
Chalfont St Giles vent shaft – Jun. 2023 (04_574)
Chalfont St Giles vent shaft looking north – May 2023 (04_573)
Section of basement floor complete and steel reinforcement in place for the remainder – May 2023 (04_572)
Sections of lining wall and base slab in place at far end of basement- May 2023 (04_571)
Steel reinforcement for base slab – May 2023 (04_570)
Top of the vent shaft – May 2023 (04_569)
Top of the vent shaft – May 2023 (04_568)
The tunnels are 26 metres below ground – May 2023 (04_567)
Chalfont St Giles vent shaft – Nov. 2022 (04_566)
Looking north-west across the Chalfont St Giles vent shaft – Nov. 2022 (04_565)
Waterproofing the vent shaft basement – Nov. 2022 (04_564)
Top section of vent shaft to be removed – Nov. 2022 (04_563)
Secant piling – Nov. 2022 (04_562)
Vent shaft diaphragm wall – Nov. 2022 (04_561)
Chalfont St Giles vent shaft – Nov. 2022 (04_560)
Vent shaft and headhouse basement – Oct. 2022 (04_554)
Chalfont St Giles vent shaft looking east – Oct. 2022 (04_553)
Chalfont St Giles vent shaft looking north across Bottom House Farm Lane – Apr. 2022 (04_552)
Chalfont St Giles vent shaft looking east – Aug. 2022 (04_551)
Looking west towards the vent shaft past Upper Bottom House Farm – Jul. 2021 (04_549)
Looking north towards the shaft and the secant piling rig – Nov. 2021 (04_533)
Balancing pond looking east – Nov. 2021 (04_531)
Secant piling rig constructing the basement – Nov. 2021 (04_527)
Looking north towards the vent shaft – Sep. 2021 (04_507)
Looking north towards Chalfont St Giles vent shaft – Sep. 2021 (04_506)
Chalfont St Giles vent shaft looking west – Jul. 2021 (04_499)
Chalfont St Giles vent shaft looking north – Apr. 2021 (04_456)
Chalfont St Giles vent shaft looking north – Apr. 2021 (04_453)
Chalfont St Giles vent shaft looking north – Mar. 2021 (04_426)
Looking west along the haul road towards the vent shaft – Mar. 2021 (04_424)
Bottom House Farm Lane drainage installation – Mar. 2021 (04_421)
Looking east from Bottom House Farm Lane across the vent shaft – Dec. 2020 (04_379)
Bottom House Farm Lane looking east – Dec. 2020 (04_378)
Looking east from Hobbs Hole across the vent shaft – Oct. 2020 (04_377)
Contractor’s (Align) welfare unit – Dec. 2020 (04_360)
Looking north towards the vent shaft – Dec. 2020 (04_346)
Looking west towards the vent shaft – Dec. 2020 (04_345)
Chalfont St Giles vent shaft looking east across the re-located welfare unit foundations – Dec. 2020 (04_344)
Chalfont St Giles vent shaft looking west across the re-located welfare unit foundations – Dec. 2020 (04_343)
Looking north towards the Chalfont St Giles vent shaft – Dec. 2020 (04_342)
Upper Bottom House Farmer’s driven to protesting – Nov. 2020 (04_331)
Haul road blockage looking west – Nov. 2020 (04_330)
Haul road blockage looking east – Nov. 2020 (04_328)
Looking north towards the vent shaft from Bottom House Farm Lane – Nov. 2020 (04_315)
Chalfont St Giles vent shaft looking east – Nov. 2020 (04_302)
Chalfont St Giles vent shaft looking north – Nov. 2020 (04_301)
Chalfont St Giles vent shaft entrance – Nov. 2020 (04_300)
Chalfont St Giles vent shaft looking north – Nov. 2020 (04_286)
Chalfont St Giles vent shaft looking north west – Nov. 2020 (04_284)
Chalfont St Giles vent shaft entrance looking east – Nov. 2020 (04_283)
Bottom House Farm Lane looking east – Nov. 2020 (04_282)
Chalfont St Giles vent shaft entrance looking north – Nov. 2020 (04_281)
Chalfont St Giles vent shaft entrance north from the haul road – Nov. 2020 (04_279)
Looking east towards the vent shaft – Oct. 2020 (04_261)
Looking north towards the vent shaft across the Fusion compound – Oct. 2020 (04_260)
Chalfont St Giles vent shaft looking north – Oct. 2020 (04_259)
Looking west along the temp. trackway – Oct. 2021 (04_258)
Looking west along the haul road towards the vent shaft – Oct. 2020 (04_257)
Vent shaft, Fusion compound and Hobbs Hole – Oct. 2020 (04_243)
Looking west past Upper Bottom House Farm towards the vent shaft – Oct. 2020 (04_242)
Looking north across the Chalfont St Giles vent shaft – Oct. 2020 (04_240)
Looking east towards the entrance to the Align compound – Sep. 2020 (04_218)
Entrance to the Chalfont St Giles vent shaft construction compound – Sep. 2020 (04_216)
Looking south from the vent shaft towards Bottom House Farm Lane – Aug. 2020 (04_200)
Looking west along the haul road, Bottom House Farm Lane and temp. access road – Sep. 2020 (04_197)
Looking west along the haul road and Bottom House Farm Lane – Oct. 2020 (04_196)
Looking north across the Fusion compound towards the vent shaft – Sep. 2020 (04_181)
Bottom House Farm Lane looking east towards temporary access road – Sep. 2020 (04_180)
Bottom House Farm Lane and temporary access road looking west – Aug. 2020 (04_148)
Looking north towards the vent shaft past Hobbs Hole and the Fusion compound – Sep. 2020 (04_183)
Hedge removal in Bottom House Farm Lane to create entrance to vent shaft – Jul. 2020 (04_124)
Bottom House Farm Lane looking east – Jun. 2020 (04_94)
Bottom House Farm Lane looking west – Jun. 2020 (04_93)
Bottom House Farm Lane looking east – May 2020 (04_82)
Bottom House Farm Lane looking west – May 2020 (04_63)
Bottom House Farm Lane looking east – Mar. 2020 (04_60)
Bottom House Farm Lane looking west – Mar. 2020 (04_59)
Looking north towards Chalfont St Giles vent shaft – Mar. 2020 (04_58)
Looking east across the Chalfont St Giles Vent Shaft – Jun. 2019 (04_557)
Looking west across the Chalfont St Giles vent shaft site towards Hobbs Hole – Feb. 2016 (04_558)
Looking east across the Chalfont St Giles vent shaft site – Feb. 2016 (04_556)
Chalfont St Giles vent shaft looking north – Aug. 2019 (04_06)
Looking west towards Chalfont St Giles vent shaft – Aug. 2019 (04_05)
Chalfont St Giles vent shaft looking north – Jun. 2019 (04_04)
Bottom House Farm Lane looking north – Jun. 2019 (04_03)
Bottom House Farm Lane looking east – Oct. 2019 (04_02)
Chalfont St Giles vent shaft looking south – Oct. 2019 (04_01)