Group take on HS2 in damage limitation exercise
A GROUP of experts, local politicians and concerned neighbours have lobbied HS2 Ltd for a raft of mitigation measures to lessen the project’s impact.
Campaigners called for a lower tunnel depth, the protection of the River Misbourne and the improvement of the roads on which HGV traffic would travel around Little Missenden at a House of Lords Select Committee meeting held on Monday November 7.
Representing campaign group Save St Giles, Rafael McDonnell said at the meeting: “The original route proposed a line bypassing the centre of the village by a depth of 100 metres, but the new route comes through the heart of the village.
“The tunnel as it passes under the centre of our village is at a depth of 19 metres which we believe, due to the geological make up of the land around Chalfont St Giles, is not sufficient. Nineteen metres is not much more than the length of this room.
“We don’t believe the full implications have been assessed in terms of when this new route was put through the heart of the village and so we’re asking for two things to be considered.
“One, the route of the tunnel is drilled deeper underneath the village and, two, the river is safeguarded to lessen potential impact on the village and the environmental impact.
“We believe to date a lot of the work that had been done was based on desk-based research.
“We feel there’s not a thorough understanding of the area, of the makeup of the soil and the surrounding land in our village.
“We feel that we cannot afford to wait and see, that some of the damage could be irreversible.”
Dr Ian Cloke, vice- president of Tullow Oil, giving evidence as a witness, said that HS2 had chosen a route ‘without sufficient study’, as the tunnel would ‘badly impact’ both the River Misbourne and Chalfont St Giles.
He argued the tunnel should be built at a minimum depth of 50 metres underground, saying the currently proposed tunnel depth of 19 metres was only 3.5 metres beneath rotten chalk.
Dr Cloke said: “It’s not until 16 metres we get into solid chalk.
“It’s a very sensitive interface. It is less than the height of a door before we get into weak ground.
“I would be very wor- ried about that if I was running the project.”
Highlighting the levels of vibration expected from a service through which 18 trains per hour would pass, he said the tunnel was only 200 metres from a listed church.
He added: “Additional tunnel depth beneath the Misbourne is essential.
“If we do this, you can mitigate chalk collapse possibility, it mitigates risk of reduction of flow of the Misbourne, it mitigates shallow fracture risk and damage to buildings, it’s deeper in the chalk and it’s away from nodules and easier to drill.
“Increasing depth below the Misbourne is simple. We believe it’s eminently achievable and the question would be, why would HS2 not do it?”
Bob Older, on behalf of the Misbourne River Action Group, argued that the proposed mitigation of the risk of loss of flow in the river due to tunnelling and vibration of trains is ‘insufficient’.
He said: “The River Misbourne is very special. It is one of the Chilterns’ chalk streams – globally rare there are fewer chalk streams in the world than there are giant pandas, and three quarters of them are in the UK.”
Mr Older argued the river provides special habitats, is a ‘much loved amenity’ and helps to define the village ‘as the community that it is’.
He also argued that sufficient measures should be taken to prevent the river from sinking into the ground.
He said that HS2 accepts a risk exists and called for the use of Bentomat lining – a geosynthetic clay liner – wherever the line crosses under the Misbourne for
Additional tunnel depth beneath the Misbourne is essential”