HS2 has announced that it has completed the first of thirty-two giant piers for the first Water Orton Viaduct, which forms part of Delta Junction, a complex network of structures in the West Midlands.

The two Water Orton Viaducts will stand twenty metres tall at their highest point, and will be among the tallest structures on the HS2 route.

Balfour Beatty VINCI (BBV) is building the northbound and southbound structures for HS2. The 1,400-metre-long viaducts in Warwickshire will carry the HS2 line which connects its Birmingham Curzon Street station with Crewe and Manchester.

Delta Junction is a triangular section of HS2 made up of nine precast segmental viaducts, embankments and other bridging structures. It will carry about ten kilometres of track crossing existing motorways, roads and rivers, taking trains over transport routes including the M42, the Birmingham-to-Peterborough rail line and the River Tame.

BBV built the pier in situ, using a formwork designed specifically for the project and a prefabricated reinforcement cage assembled in the rebar factory located near the North Warwickshire market town of Coleshill.

The piers will support the deck, which will be built in segments at HS2’s nearby purpose-built Kingsbury outdoor factory near Lea Marston, a village on the River Tame, and transported to site using haul roads in order to reduce HS2’s impact on local roads. The factory is manufacturing 2,742 segments for the entire Delta Junction, generating over six kilometres of post tensioned viaduct.

HS2’s engineers have incorporated Ground Granulated Blast-furnace Slag (GGBS) into the structures. GGBS is a by-product of steel manufacturing and reduces carbon emissions by more than sixty per cent compared with using a traditional concrete mix.

Once the piers are built, the next stage is to construct the viaduct spans by raising the segments using a temporary suspension tower erected on top of each pier. When each span is complete, engineers will take the suspension tower apart and move it along the viaduct to build the next span.

Engineers are using a ‘match-casting’ technique, in which each viaduct segment is poured against the adjacent segment in a production line. This creates a seamless viaduct deck when installed, which ensures that the whole arch fits perfectly when assembled on site. Each segment is adjustable by as little as 5mm.

Once the viaduct is built, the area beneath it will be landscaped into an accessible area with trees, new wildlife habitats, footpaths and cycle routes.

HS2 Senior Project Manager for Delta Junction, Sam Hinkley said, “This is another key moment for HS2 in the West Midlands as work ramps up on one of the most complex sections of the whole route. The Delta Junction is HS2’s key interchange where the new zero-carbon high speed railway will connect between London, the Midlands and the North.

“Minimising disruption to local communities in this area has been a key consideration in our planning, including the use of innovative pre-cast construction techniques, and haul roads to take lorries off local roads.”

David Waite, Construction Director at Balfour Beatty VINCI said: “Witnessing the removal of the shuttering to reveal the first completed pier for Water Orton Viaduct was an important occasion for the 1,100 people who make up the Delta workforce.

“With the production line at the Kingsbury pre-cast factory now in full swing, we will start to see the viaduct take shape over the coming months, with the first span due to be completed early next year.”