Colne Valley Viaduct

The Colne Valley Viaduct is one of the major elements of section C1 of the HS2 high-speed line. 3.4 km long, it crosses a series of lakes and wetlands north-west of London, in a total section of 21.6 km that also includes a twin-tube tunnel nearly 16 km long under the Chiltern Hills.

Designed to be the longest railway bridge in the United Kingdom, it is integrated into a sensitive natural environment, which required particular attention to be paid to its integration into the landscape and to limiting its impact on the environment.

VSL – in a joint venture with Keller (KVJV) – carried out major foundation and ground stabilisation works on section C1, comprising the Chiltern Tunnels and the Colne Valley Viaduct. The teams carried out geotechnical investigations, an extensive foundation testing programme, stabilisation of the south portal walls, installation of protective pile canopies, and compaction grouting operations to secure the platforms.

Built by the Align consortium (Bouygues Travaux Publics / Sir Robert McAlpine / VolkerFitzpatrick), the viaduct will accompany the gradual commissioning of the future HS2 line, which is intended to improve the capacity and reliability of inter-city travel.

The construction of the viaduct was based on extensive preparatory work, including geotechnical investigations, pile testing, soil reinforcement and stabilisation of the excavation platforms. On site, more than 1,000 precast concrete segments were assembled using the ‘Dominique’ launcher, enabling steady progress on the structure above the waterways. The operations were carried out in conjunction with the Chilterns tunnel works, the other major component of Lot C1.

This major infrastructure project, scheduled for completion in 2026, has created 16,000 jobs and freed up capacity on existing lines, both in terms of freight and passenger traffic.