Geoscience experts have used their specialist rope access skills and inflatable boats to extract concrete samples from inside Sheffield’s Megatron culvert.
The culvert is a concrete tunnel beneath Sheffield that carries the River Sheaf. The work is part of a project that has seen a section of the river uncovered for the first time in 100 years. It is located in the centre of Sheffield, where the River Sheaf meets the River Don, and is part of a larger £15 million endeavour to create a new public park.
The 70-metre-long culvert was built over a section of the River Sheaf in 1917, as part of work to create the Castle Market, at a time when the river was badly polluted with sewage and slaughterhouse run-off, according to Sheffield City Council.
RSK Geosciences project manager Stephen Owen said: “Two buildings, Alexandra House and Exchange Place Studios, stand close to the edge of the culvert. Before the culvert can be removed, it is necessary to understand what is behind the concrete and how this could affect the structural integrity of these nearby buildings.”
Stephen explained that they carried out ground-penetrating radar surveys above ground, in addition to collecting vertical and horizontal concrete cores from inside the culvert. Five horizontal concrete cores and three vertical cores were taken. Endoscope surveys of the core holes were carried out, along with covermeter surveys – a method of using electromagnetic measurements to measure the position, depth and size of the reinforcements within the concrete – of the walls, arches and roof of the culvert.
He said: “We accessed part of the culvert through a manhole, but an underground weir blocked us from going further downstream. Fellow RSK Group company CAN Structures used its expertise in rope access and confined spaces work to go up the culvert on an inflatable boat and take the surveys for this area.
“Being a river, the flow and water level can change quickly, so there were some significant health and safety precautions to be taken. There is also a nesting bat population inside the culvert, so to avoid causing disturbance we had to work outside of the hibernation season.”
Concrete quality testing was carried out on recovered samples and the data included in the final report for Sheffield City Council. This report will inform the planning and design process on how to remove the culvert without affecting the nearby buildings, Stephen said.
Sheffield City Councillor Ben Miskell, who chairs the council’s Transport, Regeneration and Climate Policy Committee said: “For more than 100 years the River Sheaf, which gave the city its name, has been covered by brick and concrete. Uncovering the river is an incredibly important milestone and just one part of the wider transformation of the Castlegate site. Our new city centre public park will also feature the remains of the city’s old 12th century castle, including the gatehouse, visible to the public. The whole area is pivotal to the history of our fantastic city and our new park will showcase this most historic of areas for decades to come.”
Removal of the culvert began in August 2024, with Sheffield City Council’s final vision due to be completed by 2026. The site will also include new buildings for commercial, community or education use. Funding for the project has already been secured through funding from central Government.
The opening up of the River Sheaf is being streamed online by the Sheaf and Porter Rivers Trust.
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