New Images – Construction of HS2’s Colne Valley Viaduct Reaches Halfway Point

New Images – Construction of HS2’s Colne Valley Viaduct Reaches Halfway Point

The largest single structure built for Phase One of the HS2 high-speed railway has passed a significant construction milestone.

HS2 Ltd recently announced that work on the Colne Valley Viaduct, set to become Britain’s longest rail bridge at 2.1 miles, has officially reached the halfway stage and released some new images. When complete, the concrete viaduct will carry trains across a landscape of lakes and waterways northwest of London at speeds up to 200 mph.

The design concept for the Colne Valley Viaduct focuses on engineering capabilities and integration with the surrounding environment of the Colne Valley Regional Park. At 3.4 km long and weighing 116,000 tonnes, the structure pushes boundaries in scale and logistics. Yet, with its graceful arches reflecting across the water, crews have aimed to complement the rural setting rather than impose upon it.

Aerial view of HS2s Colne Valley Viaduct at sunset 6 Aerial view of HS2s Colne Valley Viaduct at sunset 8 Aerial view of HS2s Colne Valley Viaduct at sunset 10

Extensive acoustic barriers along the viaduct will reduce noise emissions, while an ingenious concrete casting method ensures tight tolerances between the 1,000 prefabricated segments. These measures highlight the project’s attention to technical and ecological detail.

Workers broke ground on the Colne Valley Viaduct in early 2021, beginning the difficult task of sinking nearly 300 concrete piles to anchor the foundation. By autumn, an onsite precast factory was fully operational to start fabricating the bridge deck units. Crews are deploying specialized equipment like a 160-metre segmented launch girder to officiate units into place.

As of November 2023, crews have installed over half of the planned deck segments using match-cast techniques. At peak operation, the casting factory produces around 12 new units per week – each weighing up to 140 tonnes.

The mechanical launching system places one segment on either side of a pier in a balanced and cantilever fashion until the structure can support its weight. Officials anticipate finishing the main viaduct deck by 2024, with full completion expected in 2025 after removing temporary facilities.

Once integrated with the adjoining Chiltern Tunnel, the Colne Valley Viaduct will provide a critical link, allowing HS2 trains to maintain full speed along otherwise challenging terrain.

The project aims to spread prosperity and offer environmental benefits over alternative transit modes by improving connections between Britain’s major economic hubs.

While representing state-of-the-art engineering, the viaduct also takes place in a proud history of innovative UK bridges dating back to the Industrial Revolution. As an efficient, sustainable centrepiece of the nation’s updated rail infrastructure, the structure seems poised to serve its scenic valley for the next century and beyond.


  • Colne Valley Viaduct in west London will be the longest UK rail bridge at 2.1 miles
  • Passed the halfway point of construction in November 2023
  • Innovative precast concrete and specialized equipment enable efficient assembly
  • Projected completion by 2025 to carry high-speed HS2 trains over the scenic valley
  • Showcases possibilities of engineering integrated with environmental sensitivity
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