A structure that will be built to provide emergency access and ventilation to HS2’s 10 mile-long Chiltern tunnel has been given the green light in what is being hailed as a “major milestone” for the contentious rail line.
Buckinghamshire Council has given planning approval to one of five headhouses, which will be in Chalfont St Peter.
Taking its inspiration from the style of local barns and other agricultural buildings, HS2 says the headhouse is designed to fit into the surrounding landscape.
Set back from the road, the single-story building will be wrapped in a simple grey zinc roof with doors and vent openings picked out in a dark bronze colour to provide contrast.
The “pre-weathered” roof will age naturally over time, without loss of robustness or quality, while the whole structure will sit on a simple dark blue brick base, HS2 has said.
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Below ground level, a 78 metre ventilation shaft will reach down to the twin tunnels below, with fans and other equipment designed to regulate air quality and temperature, remove smoke in the event of a fire and provide access for the emergency services.
The firm engaged with the Chilterns AONB Review Group and Buckinghamshire Council during the development of the designs, and held a series of public engagement events to get views from the local community.
HS2 says mature trees along the existing boundary are being kept “as far as possible” and when the site is complete, new trees and hedgerows will be planted.
The high speed rail line’s project client director, Rohan Perin, said: “Planning approval for the Chalfont St Peter headhouse is a major milestone for the project and I’d like to thank all those who have helped get us to this stage.
“Throughout the design process we have been very aware of the unique rural setting of the headhouse structures and the importance of creating something that fits into the landscape.
“I’m glad that aspiration has been recognised and look forward to working closely with the council and community as we bring forward the designs for the remaining structures.”
A temporary access road to link the site with the A413, Amersham Road, has been completed, with HS2 saying it will allow construction traffic to avoid the centre of Chalfont St Peter and stop heavy goods vehicles driving past Robertswood School and the Epilepsy Society.
A new temporary marshalled lorry holding area has also been created on the A413 near Gerrards Cross.
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HGVs can be held in this newly surfaced layby until their approach to the vent shaft site is clear – helping to reduce congestion and eliminate queueing at the site entrance, HS2 says.
The two tunnel boring machines that will dig through the Chiltern tunnels are set to launch from a site near the M25 later this year.
Speaking about the design of the headhouse, Alan Price, director of Align JV Design, HS2’s main works contactor, said: “We are always very conscious of the sensitive setting for any permanent structures on the project and the Chalfont St Peter headhouse is no exception.
“As well as splitting up the buildings to create the farmyard feel, we have created a shallow basement structure to hide the ventilation equipment below ground.
“We are very pleased that this has been recognised by the local planning authority in granting this approval.”
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