Bentonite Pollution -
Chalfont St Peter Vent Shaft

FOI request to the Environment Agency

A request by Mark Keir -

"Reports on 18th June 2021 suggest that Bentonite was found leaching up to 100m from HS2 Ltd's Chalfont St Peter Air Vent Shaft. A report was filed to Environment Agency.
Please could I see a copy of this report (redacted if necessary), and please tell me what you have done/intend to do about it."    (What do they know - request page)


"We are aware of a loss of bentonite which happened during the initial walling activity in 2020. This is discussed in the report,“Analysis on Bentonite Loss during Chalfont Saint Peter D-wall excavation”, document number 1MC05-ALJ-GT-NOT-CS02_CL04-000001, dated 2 December 2020. I have attached a redacted copy of this report. (html, pdf)"

Response from the River Chess Association

"Finally we have read the conclusions and recommendations in this report and there is no mention of how this event impacts the risks associated with the HS2 Tunnelling operation. We have always said that we anticipate significant drilling and cement losses in the tunnelling operation putting the aquifer and groundwater at risk, the event at Chalfont Saint Peter vent shaft completely supports our arguments. So was this incident taken into account when the Environment Agency "approved" on 23rd April 2021 the HS2 application to start tunnelling ?"

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