Council leaders visit Britain’s longest rail bridge

Council leader Cllr Stephen Giles-Medhurst along with deputy council leader Cllr Sarah Nelmes, Cllr Louise Price, lead member for infrastructure and economic development, and Joanne Wagstaffe, Chief Executive of the district council, recently visited the South Portal site in West Hyde to see the progress of the Colne Valley Viaduct.

The viaduct is the longest in the UK, stretching more than 3.4km (2.1 miles) across a series of lakes and waterways between Hillingdon and the M25 on the northwest outskirts of London. It is longer than the Tay Bridge in Dundee, the longest railway bridge in the UK for 140 years, by just 100 metres.

The erection of the deck of the viaduct started in May 2022 by the Align joint venture delivering the central section of HS2. Align has recently completed the deck with the placement of the viaduct’s 1000th uniquely shaped deck segments, a significant moment for the project.

During the visit, councillors and the Chief Executive were shown how the South Portal construction site will become a 127-hectare haven for wildlife once the project concludes. This will involve seeding a chalk grassland mix into re-instated, low nutrient subsoils to encourage the establishment of a biodiverse chalk downland. Underlying the new grasslands is chalk excavated from the Chiltern Tunnels, and recycled concrete and aggregates from construction works, which will provide a calcareous base for the chalk-loving grassland species growing above.

It also sits alongside new areas of woodland, wood pasture and wetlands, including almost 65,000 trees and shrubs of 32 species and nearly 3.5km of new hedgerows within the Colne Valley Western Slopes. Around 4.5km of new footpath, cycling and horse-riding routes will give the public access to large parts of the site, which sits between the Colne Valley Regional Park and the Chilterns Area of Outstanding Natural Beauty.

Cllr Stephen Giles-Medhurst said: “It was fantastic to see the viaduct in person and is a triumph in engineering that sits well within the district. I congratulate the highly skilled personnel on reaching this significant milestone and I look forward to seeing the next phase of the project.

“We as a council take the green agenda very seriously, and that’s why I was pleased to see so much work has already taken place in rewilding the construction site that will see many wildlife and plants – some of which are rare - call our district their new home.”

David Emms, Project Client Director (Align), HS2 Ltd, said: “It was a pleasure to welcome Three Rivers District councillors to this HS2 site because we were able to show them the completed 2.1 mile viaduct across the Colne Valley; and how we’re using millions of tonnes of material excavated from the railway’s 10-mile long tunnel under the Chiltern Hills to recreate chalk grasslands that will be a long term community and wildlife asset.”

PHOTO CAPTION 1: (In blue helmets) Cllrs Louise Price, Sarah Nelmes, and Stephen Giles-Medhurst and Jo Wagstaffe with HS2 personnel at the Colne Valley viaduct  

PHOTO CAPTION 2: (From left) Council Leader Cllr Stephen Giles-Medhurst, Deputy Council Leader Cllr Sarah Nelmes, and Cllr Louise Price, Lead Member for Infrastructure, by the Colne Valley viaduct, which stretches for 2.1 miles

PHOTO CAPTION 3: Council Leader Cllr Stephen Giles-Medhurst (right) learning about the Colne Valley viaduct from the HS2 personnel