More concerns have been raised about HS2 digging under the Chilterns AONB amid fears it could damage Bucks rivers.

Last week the Chiltern Society warned that the chalk aquifer – which it says provides drinking water to thousands of people in the region – is “under threat” from HS2’s planned operations for the 10-mile-long Chiltern tunnels.

It said in a statement on its website: “When plans to tunnel beneath the Chiltern Hills were first announced in 2010, the Chiltern Society and others raised concerns relating to the potential for significant damage to both the chalk aquifer, which supplies drinking water to many thousands of people regionally and in London, and to the Rivers Misbourne and Chess, which are internationally rare and threatened chalk streams that rely on the aquifer to support this very special habitat, and the diverse wildlife that it supports.”

At the time, HS2 said the majority of the water used during the construction of the tunnels will be drawn from Thames Water’s supply, which “does not come from the aquifer”.

Now, Buckinghamshire Council and Chilterns Conservation Board say they have “serious concerns” about the impact of the tunnelling on Bucks’ aquifer and chalk streams.

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They said in a joint statement that the concerns relate to pollution resulting from tunnelling operations, increasing abstraction of water and impacts on the flow of significant chalk streams, such as the River Misbourne.

A spokesman said: “The council and the Chilterns Conservation Board are seeking reassurance from HS2 that worst case scenarios relating to the impacts of their tunnelling operations have been addressed.”

Bucks Free Press: PICTURED: The River Misbourne (image: Brenda Spargo, BFP Camera Club)PICTURED: The River Misbourne (image: Brenda Spargo, BFP Camera Club)

They also said they “remain unconvinced” that “HS2’s approach to monitor and mitigate impacts is sufficient”, and so are “seeking urgent answers before tunnelling operations commence”.

Ian Thompson, Buckinghamshire Council’s corporate director for planning growth and sustainibility, said: “This is a really significant issue for Buckinghamshire and both organisations share the same concerns about the potential impacts of HS2’s tunnelling operations on the county’s aquifer and chalk streams.”

Dr Elaine King, CEO at the Chilterns Conservation Board, added: “Chalk streams are a globally rare and threatened habitat. They are home to a wide range of plants and animals, and an important source of drinking water for thousands of people.

“We therefore expect HS2 to treat the chalk aquifer and these special rivers with the utmost care and respect.”

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HS2 said the 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.

A spokesman said: “We are working closely with Thames Water, Affinity Water and the Environment Agency to deliver a water supply solution that does not add any new abstraction burden to the chalk aquifer, or take any water from vulnerable chalk streams, such as the River Misbourne or River Chess. 

“As part of that work, we are looking at how we can reduce the pressure on water resources over the short to medium term and improve water supply resilience into the future.”

They added: “We have met with the Chiltern Society, River Chess Association, Buckinghamshire Council and other community groups on multiple occasions to explain our approach to tunnelling and reassure them about the protections in place.

“Ensuring the continued supply of high quality of drinking water from the chalk aquifer is an absolute priority for HS2 and we will continue to work closely with Affinity Water and the Environment Agency throughout construction to ensure any risks are managed appropriately.”