The design of the last visible part of the HS2 Chiltern Tunnel has been published.
While most of the ten-mile-long tunnel will be disguised by being built into the landscape, one part of the North Portal will be able to be seen from a footbridge.
It will be one of only seven structures of the HS2 tunnel that will be visible, with the rest of the railway being designed to blend in with the local scenery.
The North Portal, stretching between Great Missenden and South Heath in Buckinghamshire, joins headhouses above the ventilation and emergency access shafts, which will also be visible. However, the latter will be designed to look like agricultural buildings, so they do not impact the landscape.
The only other visible part of the tunnel will be the South Portal, located near the M25.
HS2 Ltd’s design director Kay Hughes said: “The Chiltern Tunnel North Portal will be one of the least visible parts of the project, but today’s reveal of the final designs is a major symbolic milestone.”
The only parts people will be able to see of the North Portal are two perforated concrete hoods that cover the track before the railway opens out from the tunnel. These are designed to avoid changes in air pressure, and reduce the noise of trains entering and leaving the structure.
There will also be a single-storey ancillary building where mechanical and electrical equipment will be stored. This will be covered in earth-coloured pigmented zinc and feature a green roof to blend in with the landscape.
Construction of the twin tunnels is well underway, as two giant tunnelling machines, named Florence and Cecilia, have been working hard removing earth between Amersham and Little Missenden.
Just last month, Florence and Cecilia had passed five miles, hitting the halfway mark after 1.5 years. The excavation of five shafts, near Chalfont St Peter, Chalfont St Giles, Amersham, Little Missenden and Chesham Road, has also been completed.
Over 1.3 million cubic metres of chalk and flint have been removed as a result, with this being saved to create a biodiverse chalk grassland, new landscape and wildlife habitat to disguise the railway.
For instance, the HS2 tunnel approaching the Wendover Dean Viaduct will be set into a cutting for 1.8 miles to hide it from public view. At the same time, 20 hectares of new woodland, wildflowers and shrubbery will be planted, with species specific to the Chilterns being used. These include Beech, Yew, Holly, Oak and Dog Rose, so the new flora and fauna remains authentic to the rest of the landscape.
Ms Hughes went on to emphasise the value of HS2’s train links in the future, saying: “HS2 will provide zero-carbon journeys across the UK, improving links between London, Birmingham and the North, while freeing up space for more freight and local services on the existing main line.”
Indeed, trains between London and the north of England will travel at speeds of up to 200 miles per hour, helping passengers journey across the country in next to no time.
HS2 believes this will “improve connections, free up space for more freight and local trains on the existing railway”.
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