Photos: First HS2 tunnel launch site

HS2 is preparing for the arrival of the project’s first giant tunnelling machines, which will be launched from a site next to the M25 early next year.

The two 2,000 tonne machines – currently being manufactured in Germany – will dig the 10-mile-long Chiltern tunnels from the site next to the M25, to near South Heath in Buckinghamshire.

Work has also begun to build the concrete precast plant where more than 118,000 tunnel segments will be made.

At 136 acres the South Portal Chalfont Lane site will be the biggest construction site on the project. From here, specialist teams will deliver the tunnelling and the construction of the adjacent Colne Valley Viaduct.

Motorway slip-roads have been built to link the new site with the M25 and take construction traffic off local roads, while material excavated from the tunnels will be reused as landscaping on site.

Around 350 staff from HS2’s main works contractor, Align JV – a team made up of Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick, and its subcontractors – are now permanently based on site.

The ‘twin bore’ Chiltern tunnels will be the longest and deepest tunnel bores on route, with separate northbound and southbound tunnels and five ventilation shafts.

Just south of the tunnel portal, the Colne Valley Viaduct – designed by Align, working with its design partners Jacobs and Ingerop-Rendel, and the architect Grimshaw – will be the longest railway viaduct in the UK at 3.4km.

HS2 delivery director, David Bennett said: “The south portal site will have one of the most important parts to play in the story of HS2. From here we’ll manage the construction of the Chilterns tunnel and the iconic Colne Valley viaduct.

“It’s great to see how much progress has been made on site – and I look forward to working with the team to deliver what will be two of the most exciting and ambitious engineering challenges on the project.”

Daniel Altier Align JV project director said: “Significant planning and preparation has been completed by the Align team, working in close cooperation with HS2 and it’s great to see developments at the south portal. We now have a significant presence on-site and this is set to increase over the weeks and months ahead. 

"This is a complex project and it’s both rewarding and exciting for the team to see the component parts coming together after all their detailed planning. Align is now actively recruiting to build our team to address the complex engineering challenges associated with the delivery of this iconic project.”