Milestone
HS2 completes three Solihull viaducts on Interchange approach
By Staff Writer | 16 August 2026
Three viaducts on the southern approach to HS2's Interchange station are now structurally complete, all of them within the Solihull metropolitan borough.
The completion was announced on 12 August 2026. The three structures are the Balsall Common, Marsh Farm and River Blythe viaducts, and they were built by HS2's construction partner Balfour Beatty VINCI on the West Midlands section of the route.
River Blythe Viaduct is the largest of the three and the closest to Interchange station, roughly a mile and a half away. It is 495 metres long and 12 metres high, and its deck is carried on two abutments and 19 concrete piers. The piers were built with Y-shaped splits to cut the volume of concrete used. The River Blythe is designated a Site of Special Scientific Interest, and the low-lying form of the structure was adopted for that reason as it crosses the river, the floodplain and Meriden Road near Hampton in Arden. The space beneath the deck was designed to allow passage for badgers, bats, birds, fish, great crested newts, otters and water voles.
Engineers were due to install the final parapets on the River Blythe structure within days of the announcement. The parapets are polished concrete and acoustic, chosen partly to cut noise for nearby residents and partly to reduce the apparent mass of the structure. Local residents were consulted on the parapet size and on the tree planting intended to settle the viaduct into the landscape. Both the River Blythe and Balsall Common viaducts were classed as Key Design Elements, a category applied where a structure's size, its closeness to communities or its position in a sensitive area marks it out, and which brought local communities into the design.
Balsall Common Viaduct sits just outside the residential area of Balsall Common village, north-east of the existing Network Rail line. It is 430 metres long and eight metres high, and it crosses Station Road, Truggist Lane, Bayleys Brook, the Heart of England Way and the associated floodplain. Its main structure was finished earlier this year. Parapet installation now begins, and all 304 of them are to be in place by spring 2027. A public vote settled the design: a polished finish to reflect the sky and surrounding vegetation, with a weave motif drawn from the area's textile history.
Marsh Farm Viaduct, two and a half miles south, is the smallest of the three. At 145 metres long and standing five metres above ground, it carries the main line over Bayleys Brook and the marshland around it. It was the first of the three to reach completion, in summer 2025, and is currently serving as a haul road for the construction of the adjacent embankments and cuttings, which keeps lorry movements off local roads.
Doug Barnett, HS2 Ltd's senior project manager, said: "The design and landscaping solutions were of upmost importance to local residents, and we worked extremely hard to get that right."
What the practitioner should take from this
Structural completion on a viaduct is a commercial event as much as an engineering one, and three of them completing together on one approach concentrates the effect.
The first question is what follows the structure. Parapets, waterproofing and acoustic barriers are finishing operations carried out by different trades on a deck that is now handed on. Where the structural package is certified complete and the finishing package cannot start on the date the programme assumed, the delay sits at the interface between two subcontracts. Whether it is recoverable turns on whether the access dates were written into each subcontract or only into the main programme.
The second is the treatment of a completed structure used for something else. A viaduct serving as a haul road is carrying loads its permanent design never contemplated, and the party using it in that way is usually not the party that built it. The condition survey taken before the haulage started, and the loading limits agreed at the time, are the documents that decide any later argument about damage. They are cheap to take and impossible to reconstruct.
The third is design settled by consultation. Where a parapet finish or a motif has been chosen by public vote, the specification has a provenance outside the contract documents. That matters when the finish proves harder to achieve than priced, or when the vote postdates the tender. The question to ask is when the requirement entered the contract and by what instrument, because the answer decides whether the cost sits with the contractor or with the employer.
None of that reflects on this project, where no dispute has been reported. It is the ordinary commercial shape of a structure signed off in stages, and the moment to check the paperwork is the moment a stage is certified, not the moment somebody complains.