HS2 engineers have completed three major structures on the southern approach to Interchange station, in the West Midlands.
The viaducts – in Balsall Common, Marsh Farm and River Blythe – are all within the Solihull metropolitan borough.
In the coming days, crews working for HS2’s construction partner, Balfour Beatty Vinci, are due to install the final parapets on the River Blythe Viaduct – the largest of the three bridges that carry the high-speed railway through Solihull.
Marsh Farm Viaduct was the first of the neighbouring structures to reach completion in summer 2025. The main structure of Balsall Common Viaduct was finished earlier this year, and all 304 parapets will be installed by spring 2027.
HS2 Ltd’s senior project manager Doug Barnett, said: “Our engineering teams are making fantastic progress on the Interchange Station approach, and it’s a significant achievement that all three viaducts in the Solihull borough are now structurally complete.
“The design and landscaping solutions were of upmost importance to local residents, and we worked extremely hard to get that right.”
Both the River Blythe Viaduct and Balsall Common Viaduct are ‘Key Design Elements’ (KDEs), which means their size, proximity to communities, or location within sensitive areas, marked them out as significant. Local communities therefore helped to influence their design.
As the River Blythe is designated as a Site of Special Scientific Interest (SSSI), the 495m viaduct was built with this in mind. The low-lying 12m-high structure skims the landscape as it crosses the river, the floodplain and Meriden Road near Hampton in Arden.
The deck is supported by two abutments and 19 concrete piers with Y-shaped splits to reduce the volume of concrete and enhance the aesthetic appeal.
Balfour Beatty Vinci construction manager Matthew Parkes said: “The structural completion of these viaducts is a another huge achievement for Balfour Beatty Vinci and its supply chain partners.
“All three viaducts span a range of diverse landscapes and environments, including wetlands, foodplains, SSSIs and water courses – making this achievement even more remarkable.”
He added: “Every effort has been made to protect these precious spaces and habitats. The realignment of Bayleys Brook is just one example of how the team has delivered on this commitment, where engineers carefully diverted a 150m section of the brook to allow Balsall Common Viaduct to pass over the top.”
The HS2 route has more than 500 bridging structures – including over 50 major viaducts which will stretch for a combined total of 15km across valleys, rivers, roads and flood plains.
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Facts Only
* HS2 engineers completed three major structures on the southern approach to Interchange station.
* The viaducts are located in Balsall Common, Marsh Farm, and River Blythe.
* All three viaducts are within the Solihull metropolitan borough.
* Crews for Balfour Beatty Vinci are installing final parapets on the River Blythe Viaduct.
* Marsh Farm Viaduct reached completion in summer 2025.
* The main structure of the Balsall Common Viaduct was finished earlier in the year.
* All 304 parapets will be installed by spring 2027.
* The River Blythe Viaduct is the largest of the three bridges.
* Both the River Blythe and Balsall Common Viaduct are 'Key Design Elements' (KDEs).
* The River Blythe Viaduct, being 495m long, was built considering its designation as a Site of Special Scientific Interest (SSSI).
* The River Blythe Viaduct deck is supported by two abutments and 19 concrete piers with Y-shaped splits.
* Engineers diverted 150m of Bayleys Brook to allow the Balsall Common Viaduct to pass over it.
Executive Summary
Full Take
The narrative highlights a process where large-scale infrastructure development intersects with localized environmental and community concerns, suggesting that achieving structural completion does not equate to full societal consensus or seamless integration. The distinction between physical construction milestones (structural completion) and final aesthetic/environmental resolution (parapet installation, landscape design) reveals a gap in the timeline of public engagement. The fact that specific structures are designated as 'Key Design Elements' because of community input suggests a mechanism where local influence is acknowledged post-design selection, rather than being fully integrated prior to execution. The focus on protecting SSSIs and managing watercourses points toward a tension between engineering objectives and ecological preservation—a balance that requires sustained oversight beyond the initial project phase. Furthermore, the reported effort to realign natural features like Bayleys Brook demonstrates that mitigating environmental impact often becomes an add-on process rather than a foundational constraint, raising questions about whether these measures are sufficient or indicative of a pattern where environmental protection is reactive rather than proactive in large infrastructure planning. The persistence of needing final installations, such as parapets, late in the timeline suggests that accountability shifts from structural integrity to surface quality and contextual sensitivity once the primary engineering goal is met.
* BRIDGE QUESTIONS: If design elements are determined by community influence, what formal governance structure ensures ongoing, binding engagement throughout the phased construction? How can the protection of SSSIs be embedded as a non-negotiable baseline rather than an ancillary mitigation strategy during project initiation? What metrics exist to evaluate the success of environmental realignments like the Bayleys Brook diversion beyond mere physical passage?