Little Missenden 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 fourth of these will be alongside the A413 in Little Missenden.

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 vent shaft depth is 31 metres and the tunnels are 24 metres below the ground. The tunnel boring machines reached here in June 2023. The vent shaft is due to be completed by April 2025. The site will also house an auto-transformer station.

PRoW LMI 40/2 will be temporarily re-routed around the construction compound. The approved access route is via the A413, A355 to Beaconsfield then the A40 and the M40. Traffic arriving at the site will do so via a temporary traffic light controlled right hand turn across the dual carriageway.

North of the vent shaft the route continues up the hill passing under the Chiltern Railway Line on its way towards the Chesham Road intervention shaft. This will be one of the steepest gradients on the whole of Network Rail.

* On November 7th 2023 a sinkhole opened up above one of the TBMs alongside PRoW GMI 27/1 adjacent to Hedgemoor Wood to the south of Hyde Lane, Hyde End.
The footpath was closed and the area fenced off. Remedial works were completed and the footpath was reopened within six weeks.

Little Missenden vent shaft looking west – May 2016 (06_190)
Little Missenden vent shaft looking north – May 2016 (06_191)
Little Missenden vent shaft looking west as construction of the headhouse gets under way – Jan. 2024 (06_227)
PRoW GMI 27/1 looking south from Hyde Lane – Dec. 2023 (06_226)
PRoW GMI 27/1 looking south towards Hedgemoor Wood and the sink hole – Dec. 2023 (06_225)
Sink hole in PRoW GMI 27/1 – Dec. 2023 (06_224) Mike Johnstone
PRoW GMI 27/1 Back filling sink hole – Dec. 2023 (06_223) Mike Johnstone
PRoW GMI 27/1 Awaiting final concreting and re-seeding – Dec. 2023 (06_222) Mike Johnstone
Little Missenden vent shaft looking north – May 2016 (06_191)
Looking south across the vent shaft towards the A413 – Oct. 2023 (06_221)
The top of the vent shaft – Oct. 2023 (06_220)
Construction of basement plenum walls – Oct. 2023 (06_219)
Crash deck removal inside the shaft – Oct. 2023 (06_218)
Looking north across the basement towards the vent shaft – Oct. 2023 (06_217)
The top of the vent shaft at basement level – Oct. 2023 (06_216)
Little Missenden vent shaft looking west – Jun. 2023 (06_215)
Looking north across the A413 towards Little Missenden vent shaft – May 2023 (06_206)
Top of the Little Missenden vent shaft – May 2023 (06_205)
Little Missenden vent shaft – Jun. 2023 (06_214)
Top section of the diaphragm wall awaiting removal – Jun. 2023 (06_213)
Preparing for the installation of shaft lining wall at level six – Jun. 2023 (06_212)
Top section of the diaphragm wall awaiting removal – Jun. 2023 (06_211)
Looking north towards the top of the shaft – Jun. 2023 (06_210)
Looking to the southern end of the basement – Jun. 2023 (06_209)
Installation of water proof membrane below the base slab and behind the lining wall – Jun. 2023 (06_208)
Looking north into the basement – Jun. 2023 (06_207)
Little Missenden vent shaft looking north from the A413 – Dec. 2022 (06_204)
Little Missenden vent shaft looking north – Dec. 2022 (06_203)
Headhouse basement construction alongside the shaft – Oct. 2022 (06_201)
Excavation of shaft completed – Aug 2022 (06_200)
Little Missenden vent shaft looking east – Jun. 2022 (06_198)
Little Missenden vent shaft looking north – May 2022 (06_197)
Shaft excavation & secant piling for basement – May 2022 (06_196)
Little Missenden vent shaft north – Apr. 2022 (06_193)
Little Missenden vent shaft looking north – Nov. 2021 (06_189)
Little Missenden vent shaft looking south – Nov. 2021 (06_188)
A413 looking north – Jan. 2022 (06_180)
A413 looking north – Nov. 2021 (06_173)
A413 looking south – Nov. 2021 (06_171)
Little Missenden vent shaft looking south – Nov. 2021 (06_170)
Diaphragm wall cutting rig – Nov. 2021 (06_169)
Hydraulic grab used to dig the first six metres of each diaphragm wall panel – Nov. 2021 (06_168)
Cutting diaphragm wall panels – Nov. 2021 (06_167)
Cutting diaphragm wall panels – Nov. 2021 (06_166)
Storage silos – Nov. 2021 (06_165)
GFRP (glass fibre reinforced plastic) reinforcing frame – Nov. 2021 (06_163)
These are used where the TBMs will cut into the shaft- Nov. 2021 (06_162)
Slurry treatment plant – Nov, 2021 (06_161)
Slurry treatment plant – Nov. 2021 (06_159)
Slurry treatment plant – Nov. 2021 (06_158)
Bentonite slurry treatment plant – Nov. 2021 (06_157)
Concrete delivered from the south tunnel portal batching plant – Nov. 2021 (06_156)
Concrete pouring directly into a diaphragm wall panel – Nov. 2021 (06_155)
Removing the concrete pouring tube – Nov. 2021 (06_154)
Removing a section of the concrete pouring tube – Nov. 2021 (06_153)
Wheel washing prior to leaving site – Nov. 2021 (06_152)
Evening working with the concrete pour – Nov. 2021 (06_150)
Little Missenden vent shaft looking north – Oct. 2021 (06_141)
Little Missenden vent shaft looking north – Oct. 2021 (06_138)
A413 looking north – Oct. 2021 (06_137)
Little Missenden vent shaft looking north – Oct. 2021 (06_136)
Preparing to install traffic lights on the A413 – Oct. 2021 (06_131)
Looking east across the A413 towards the compound entrance – Oct; 2021 (06_130)
Looking north from the A413 towards Little Missenden vent shaft – Oct. 2021 (06_128)
Looking north towards Little Missenden vent shaft – Oct. 2021 (06_127)
Little Missenden vent shaft looking south along PRoW LMI 40/2 – Sep. 2021 (06_120)
A413 looking north – Aug. 2021 (06_116)
A413 looking north – Aug. 2021 (06_115)
A413 looking north – Aug. 2021 (06_113)
A413 looking south – Aug. 2021 (06_112)
Little Missenden vent shaft looking north from the A413 – Jul. 2021 (06_109)
Little Missenden vent shaft north west – Jul. 2021 (06_102)
Little Missenden vent shaft looking east – Apr. 2021 – (06_99)
Little Missenden vent shaft looking north – Jun. 2021 (06_98)
Little Missenden vent shaft looking north – Jun. 2021 (06_96)
A413 looking north – Jun. 2021 (06_95)
Little Missenden vent shaft north – May 2021 (06_90)
Little Missenden vent shaft north – May 2021 (06_88)
A413 looking north – Apr. 2021 (06_82)
PRoW LMI 40/2 looking north – Apr. 2021 (06_80)
PRoW LMI 40/2 looking north – Apr. 2021 (06_79)
PRoW LMI 40/2 looking north – Apr. 2021 (06_78)
PRoW LMI 40/2 looking north – Apr. 2021 (06_76)
PRoW LMI 40/2 looking south – Apr. 2021 (06_75)
Little Missenden vent shaft looking north – Apr. 2021 (06_71)
Little Missenden vent shaft looking north – Apr. 2021 (06_69)
Little Missenden vent shaft looking north across the A413 – Mar. 2021 (06_66)
Little Missenden vent shaft compound entrance from the A413 looking east – Mar. 2021 (06_65)
Looking north across the A413 towards vent shaft – Mar. 2021 (06_60)
Little Missenden vent shaft looking north – Mar. 2021 (06_58)
A413 looking south towards the compound entrance – Mar. 2021 (06_56)
Little Missenden vent shaft looking east – Mar. 2021 (06_55)
Little Missenden vent shaft looking north – Feb. 2021 (06_52)
Little Missenden vent shaft looking north – Feb. 2021 (06_50)
A413 looking north – Feb. 2021 (06_49)
Little Missenden vent shaft entrance looking north – Feb. 2021 (06_48)
Little Missenden vent shaft looking north – Feb. 2021 (06_47)
Little Missenden vent shaft looking north – Dec. 2020 (06_34)
Little Missenden vent shaft looking north – Dec. 2020 (06_33)
PRoW LMI 40 looking north – Dec. 2020 (06_32)
PRoW LMI 40 looking south – Dec. 2020 (06_30)
Looking west across the Little Missenden vent shaft – Dec. 2020 (06_29)
A413 showing long term lane closure looking north – Nov. 2020 (06_27)
Re-positioned entrance to Little Missenden vent shaft from the A413 looking south – Nov. 2020 (06_25)
Little Missenden vent shaft looking north from the A413 – Nov. 2020 (06_24)
PRoW LMI 40/2 from A413 – Nov. 2020 (06_23)
Little Missenden vent shaft looking north – Nov. 2020 (06_21)
Little Missenden vent shaft looking north – Nov. 2020 (06_20)
Little Missenden vent shaft looking east – Oct. 2020 (06_18)
Little Missenden vent shaft looking north – Oct. 2020 (06_17)
Little Missenden vent shaft looking north – Jun. 2020 (06_15)
Little Missenden vent shaft looking south – Jun. 2020 (06_14)
Little Missenden Vent Shaft looking west – May 2016 (06_12)
Little Missenden Vent Shaft looking north – May 2016 (06_10)
A413 looking north – May 2019 (06_09)
A413 looking north – May 2019 (06_08)
A413 looking north – Jul. 2016 (06_07)
Little Missenden Vent Shaft looking north – Aug. 2011 (06_06)
Little Missenden Vent Shaft looking north – Jun. 2018 (06_04)
A413 looking north – May 2019 (06_03)
Little Missenden Vent Shaft looking north – Apr. 2019
Little Missenden Vent Shaft looking north – Apr. 2019 (06_01)