HS2 has shown off the final design for its ‘barn design’ headhouses that will provide ventilation and emergency access to the Chiltern tunnel just outside the M25 motorway.
To fit in with the local countryside, the Chalfont St Giles headhouse will have its surface buildings disguised to look like country barns and other agricultural buildings. Like a nearby headhouse at Chalfont St Peter, the single-story building will be wrapped in a grey zinc roof with doors and vent openings picked out in a dark bronze colour to provide contrast.
Below ground level, a 43-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.
Mature trees along the existing boundary will be retained as far as possible and once construction is complete the whole site will be landscaped with new trees and hedgerows planted to help screen the site from neighbouring properties.
Material excavated from the shaft will be used to create much of the landscaping for the site, which will then be replanted to create a wildlife haven.
There will be an online presentation about the new structure later this week.
The two tunnel boring machines that will excavate the Chiltern tunnels are set to launch from a site near the M25 later this year.
