Close-out of works on the project’s longest tunnel brings to an end a programme that began almost five years ago.
With civil works now finished, the tunnel will move into mechanical, electrical and plumbing installation, with enabling works already under way.
Track and overhead line equipment will follow as HS2 continues construction across the rest of the route.
Despite the milestone, HS2 stressed that significant work remains across the route. Chief executive Mark Wild is overseeing a full reset of the programme aimed at tightening delivery and driving down costs on the remaining sections, which is due to be unveiled within weeks.
HS2 also announced early achievement of two significant employment milestones across the project. It has just exceeded its target of creating 2,000 apprenticeships and over 5,000 unemployed have progressed into jobs.
Chiltern Tunnel drive
Main construction of the 10-mile long twin-bore tunnel started in May 2021 with the staggered launch of two 2,000-tonne tunnel boring machines from a site near the M25 at Maple Cross, Hertfordshire.
The TBMs advanced north at an average rate of 16 metres per day before breaking through near Great Missenden in early 2024. Since then, teams have completed portal extensions, installed internal walkways and fitted out 40 cross passages.
The Chiltern tunnel is the second of HS2’s five twin-bore tunnels to reach structural completion, following the one-mile Long Itchington Wood tunnel in Warwickshire last year.
Construction of the Chiltern tunnel was led by Align JV between Bouygues Travaux Publics, Sir Robert McAlpine and Volker Fitzpatrick.
Align JV project director, Adrien Baudard said: “Being part of the successful delivery of the Chiltern tunnel has been a source of immense pride for everyone at Align and our partners across the supply chain.
“Their unwavering commitment, technical skill, and collaborative spirit have been truly impressive. Whether it was advancing safety standards, setting new TBM records, or helping to train future engineers, we’ve had the privilege of learning from and working with some of the top talent in our field.
“With the completion of the Chiltern tunnel’s civil works, the achievements of this integrated project team as well as the sustainable benefits such as carbon reduction and safety innovations will set a standard in tunnelling for generations to come.”
