HS2 Ltd has the powers to take the length of the river Misbourne in Chalfont St Giles into its possession under the High Speed Rail (London-West Midlands) Act 2017.
In an announcement, Chalfont St Giles Parish Council said it received a letter titled ‘notification of service of temporary possession notices over the land at the village pond and Riverside Walk’.
It said HS2 does not require the land for works, but that it needed to take possession of the land “should the tunnelling works have a detrimental effect on the flow of the river Misbourne to the extent that corrective works are then required”.
Earlier this month, HS2 rebuffed claims from campaigners that its tunnelling risked damaging the chalk aquifer. The Chiltern Society said that the "fragile chalk aquifer beneath the Misbourne Valley – which provides drinking water to thousands of people in the region – is under threat from HS2 Ltd's planned tunnelling operations".
But HS2 dismissed the claim, saying that their tunnel boring machines "have been specifically designed to operate in this geology with an expert team monitoring their progress to ensure that there isn't damage to the aquifer".
Conservationists and many in the surrounding communities say they have three main concerns. The first is that the estimated millions of litres of water – needed every day to facilitate the drilling – will bleed the already depleted aquifers dry, and result in further damage to the region’s chalk streams.
The second is that slurry, which will be removed from the tunnels during tunneling and be put through various treatment processes such as holding lagoons, will hold such tiny particles in suspension it will be impossible to remove them when it is returned to the river, harming wildlife.
A final concern is that the tunneling process will mobilise pollutants in the chalk, such as chemical run off from farms, that will make their way into the aquifer, contaminating drinking water.
According to the parish council, the tunnelling works will be below Chalfont St Giles from 22 August 2022 for 12 days, but this schedule may vary as the tunnel boring machine progresses.