Contractors building a new HS2 viaduct made history today as they lowered the final section of the deck into place in a venture that is crowning it as Britain’s longest new railway bridge.
The gently curving 3.4 km (2.1 mi) long structure on the northwest edge of London stretches across the Colne Valley close to the M25 motorway and the village of Denham. It will carry high-speed trains to and from the capital at speeds of up to 320 km/h (200 mph).
The viaduct’s completion means the 3.3km Tay Bridge linking Fife and Dundee has finally ceded the crown of Britain’s longest railway bridge to HS2, a record it had held since 1887.
Construction of the Colne Valley Viaduct is being managed by main works contractor Align JV – a team comprising Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick. It is one of 500 bridging structures on the HS2 project which also includes footbridges, drainage culverts and innovative ‘green bridges’ for wildlife.
Construction work on the viaduct deck began in May 2022. Over the next 28 months a dedicated team of highly skilled engineers used a huge launch beam to lower the 1,000 uniquely shaped bridge deck sections into place.
Moving forward from north to south and resting on the viaduct’s 56 piers, the 160m long launcher used a balanced cantilever method to lower the deck sections into position to form a half arch on either side of one pier before moving to the next pier to complete the arch opening by repeating the process.
The 1,000 prefabricated sections are manufactured on site in a purpose-built factory. Each of the sections is uniquely shaped to allow the structure to curve as it carries the high-speed line up to 10 meters above land and water across the Colne Valley.
Once the main phase of civil engineering is finished, the factory and surrounding buildings will be removed and the entire area between the viaduct and HS2’s 10-mile tunnel under the Chiltern Hills just to the north will be turned into an area of chalk meadows and woodland as part of HS2’s ‘green corridor’ project.
Construction of the viaduct will then move into the rail systems installation phase as it moves towards becoming an operational part of the new high-speed rail between 2029 and 2033.
HS2 Ltd Senior Project Manager Billy Ahluwalia said: “The lowering of the final deck section of the Colne Valley Viaduct today marks the culmination of over 10 years of planning, design and construction. I pay tribute to the dedicated team who have delivered a bridge that is both the longest on HS2 and has become the longest bridge in the UK.” 140 years this is a historic achievement of which we can all be very proud.”
Align Project Manager, Loïc Menard commented: “The Align team, along with the VSL supply chain partners who handled the launch beam, have worked very hard to get us where we are today, ahead of schedule. Working together and as a truly integrated team that includes HS2, Align, our design partners, our supply chain colleagues and the local Valley community, which will is the local HS2 community.”
The milestone comes a week after the completion of HS2’s first major viaduct, at Highfurlong Brook in Northamptonshire. Work is also progressing on the Delta Junction viaducts in the West Midlands and the elevated approaches to Curzon Street station.
Image credit: HS2
