Barhale has scooped a £22 million programme of inspections and works on the Thames Water Ring Main (TWRM) and Raw Water tunnels.

Under the Thames Water Tunnels and Aqueducts Programme, the civil and infrastructure specialist will carry out monitoring and maintenance on a total of 35km of ring main tunnels and a further 9km of raw water tunnels. Associated works include the refurbishment of four High Integrity Valves (HIVs) and relining a 1.8km length of the 2.5m inlet and outlet tunnels for the QEII Reservoir at Walton-on-Thames.

The TWRM is an 80km long, 2.5m diameter tunnel built between 1988 and 1994 to take water from five treatment works and transfer flows via pumping stations housed in shafts along the route. It is a major part of London’s water supply infrastructure and carries an average daily flow of 0.3 x109 gigalitres – a little under one-sixth of the capital’s daily demand.

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Phil Cull, Barhale's Southern Region Director said: "Under AMP6 we worked closely with the Thames Water team to refurbish 19 of the 22 shafts. It's meant that we have gained insights and knowledge of working across the Ring Main that is second-to-none. We are very pleased that experience has been recognised by Thames Water and to be given the go-ahead on this important programme of works.

"The TWRM and the raw water tunnels are absolutely critical pieces of infrastructure for London and the scale of the task cannot be underestimated. To put it in perspective, one element of the programme of works will be the replacement of all of the grout hole caps along 27km of tunnel – a total of 217,000 at around 8 per metre."