Viaduct deck segments are made using a ‘match-casting’ technique - where each segment is poured against the previous one, ensuring the whole deck fits perfectly when assembled on the piers. The mammoth 100m-long temporary viaduct precast factory with a volume of 105,000 cubic metres is larger than the Royal Albert Hall.

In Spring 2021, our two Tunnel Boring Machines (TBM), Florence and Cecilia began their 10-mile journey under the Chiltern Hills. This is the launch of TBM Florence from the South Portal.

Segments that will line the tunnels are produced on site at the South Portal in our pre-cast factories. Each segment weighs up to 8 tonnes. 112,000 segments are needed to build the Chiltern Tunnels.

A peek inside the Chiltern Tunnel.

We are constructing 38 cross passages linking the northbound and southbound tunnels. This is a cross passage at waterproofing stage.

We have five Shaft sites along the Chiltern tunnel route for ventilation and access. All five Shafts have been excavated. This is a view from the bottom of the Amersham shaft.

Chalk excavated from the Chiltern tunnels being used to landscape the site which is set to become a 127 hectare wildlife haven featuring new chalk grassland, woodland, wood pasture and wetland habitats.

In May 2022, we launched ‘Dominique’ the Launching Girder that will install the deck segments for the 3.4km Colne Valley Viaduct.

Viaduct deck segments are made using a ‘match-casting’ technique - where each segment is poured against the previous one, ensuring the whole deck fits perfectly when assembled on the piers. The mammoth 100m long viaduct precast factory with a volume of 105,000 cubic metres is larger than the Royal Albert Hall.

Our temporary access bridge, which was completed in February 2022 to support the construction of the Colne Valley Viaduct, has already taken more than 10,000 vehicle journeys off local roads in its first year of operation. The 800m long temporary bridge, is also used to get equipment out to where the viaducts piers are being built in the lake.

The Colne Valley Viaduct will be the longest railway bridge in the UK once complete. Over 500, out of a thousand deck segments, have now been installed (October 2023), with each one weighing up to 140 tonnes. To allow for the gentle curve of the viaduct as it crosses the valley, each segment is unique.

Work on the Shaft Headhouses is now underway, this is Chalfont St Peter shaft Headhouse in September 2023. The headhouses were designed in consultation with local communities, our priority has been to blend the buildings into their surrounding landscape, taking inspiration from the style of local barns and other agricultural buildings.

Work began on the Porous Portal in early 2023. Designed to cut noise from trains entering and exiting the Chiltern tunnels, two perforated concrete hoods will cover the track, extending the 10 mile long tunnel into the open air. These porous portals will avoid sudden changes in air pressure – and resulting noise – caused by trains entering and exiting the tunnels

In February 2024, TBM Florence completed her 10-mile journey under the Chiltern Hills. Colleagues from Align, HS2 and our Supply Chain were there to witness the moment she broke through at the North Portal.

Members of the Align Tunnelling team celebrating the safe arrival of our second TBM Cecilia in March 2024 having also completed her 10-mile journey under the Chiltern Hills.

In early September 2024, the final deck segment of the 3.4km Colne Valley Viaduct was installed. The team gathered to celebrate this historic moment as the Colne Valley Viaduct is now the longest rail bridge in Britian breaking the record held by the 3.3km Tay Bridge linking Fife and Dundee since 1887.