HS2 celebrates big carbon saving on UK's longest rail bridge

The HS2 Colne Valley Viaduct (CGI from Jacobs)

Deputy Chief Executive at the Infrastructure & Projects Authority, Matthew Vickerstaff, joined Future Cities Forum discussions last week on 'The making of the modern city' at abrdn PLC and commented on the speed at which the HS2 construction phase was progressing.

He was invited to talk as part of our ongoing series of debates and reports around the economic levelling up of the UK. Future Cities Forum will be taking its discussions this year to Manchester, Leeds and Birmingham to understand the different perspectives of local authorities and investors who are involved in the levelling up agenda for their cities.

HS2, although attracting criticism from some quarters over cost and environmental issues, is moving forward with the aim of levelling up parts of the country and in particular reducing commuting times between large cities such as London and Birmingham - and bringing economic and social benefits to businesses and communities around Crewe and Solihull - where there will be additional stations..

Part of HS2 has involved the design and construction of the Colne Valley Viaduct which the engineering firm Jacobs has been involved in, tracking the amount of embedded carbon in the Viaduct - which is at least 28.4%, as works continue for what will be the UK's longest railway bridge.

The firm states:

'Applying lessons from the construction of the latest European high speed railway bridges, the team has cut the amount of embedded carbon in the viaduct by 63,000 tonnes of CO2e - the equivalent of 234,500 flights from London to Edinburgh.

'HS2 Ltd's main works contractor Align JV - a team made up of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick - worked for four years on the design with Jacobs and Ingerop-Rendel as design partners and architects Grimshaw.

'Starting from the reference design produced as part of the HS2 parliamentary process, the team refined the design, challenged assumptions, and found efficiencies to help reduce the amount of steel and concrete in the structure. This included working closely with rail systems experts at HS2 Ltd to allow the structure to be narrowed by over one meter, while still allowing sufficient space for signalling and control equipment alongside the line. They also worked to bring the northbound and southbound tracks closer together further north, which in turn significantly reduced the amount of earthworks required for the approach embankment.

'Narrowing the width of the viaduct allowed a significant reduction in carbon emissions and helps reduce disruption for local residents by reducing the number of heavy goods vehicles on local roads.

'Inspired by the flight of a stone skimming over the surface of the water, the Colne Valley Viaduct will stretch for 3.4 kilometers (2.1 miles) across a series of lakes on the outskirts of London, and will be one of the most high-profile structures on the new HS2 Phase 1 between London and Birmingham.

'Every element of the design was challenged during the design process, with noise barriers moving from solid concrete to a composite design with noise absorbing steel cassettes at the bottom and transparent acrylic at the top, helping to reduce the amount of concrete while also reducing the visual weight of the structure and enabling views across it.

'An extensive programme of test piling was also completed ahead of the start of construction with geological and structural data from these tests fed back into the design of the viaduct. This has resulted in a 10-15% reduction in the depth of the piles and associated time, cost and carbon savings.'

'By providing a cleaner, greener way to travel, HS2 will help cut the number of cars and lorries on our roads, cut demand for domestic flights, and help the fight against climate change.' commented HS2 Ltd Senior Project Manager Billy Ahluwalia.

Jacobs Technical Director David Sizer says:

'As Carbon Manager and Life-Cylce Analysis (LCA) Practitioner for Align, Jacobs prepared the carbon and LCA baseline - reassessing the updated design at each project gateway. We developed the carbon management plan encompassing carbon reduction targets, savings opportunities, stakeholder and supply chain engagement and training needs. We also implemented a PAS2080 Carbon Management in Infrastructure compliant process with Align, independently verified by the British Standards Institute, with has provided the framework for the whole value chain to focus on lower carbon solutions.'

Future Cities Forum will be running its infrastructure development, transport ands energy forum in February. Join us then for more debate.