en.Wedoany.com Reported - UK-based Barhale has secured a contract from Thames Water to replace the lining of a section of the intake tunnel at the Ashford Common Water Treatment Works (WTW) in Surrey, England. The project aims to maintain the structural integrity of London's water supply network.
The Ashford Common WTW is supplied by reservoirs in the West London Abstraction area (WLA), which are connected via a network of tunnels and trunk mains, providing water to multiple treatment sites. During a statutory five-year inspection, Barhale's Tunnels & Aqueducts team identified inconsistencies in an existing glass-reinforced plastic (GRP) lining in a section of the Southern Inlet tunnel. Inspection results indicated that these irregularities could potentially damage the underlying wedge block tunnel. Under the new contract, works will involve replacing only the affected lining section of the tunnel. According to Barhale, the company initially collaborated with Thames Water during the Early Contractor Involvement (ECI) phase to develop a feasible plan addressing the restricted access within the multi-level tunnel network beneath Ashford Common.
The lining replacement process is planned to commence with excavation to a depth of 3 meters to expose the shaft and riser. Selected sections of the riser will then be removed to allow safe descent to the tunnel invert, located 19.5 meters below ground. Subsequently, scaffolding will be installed to provide safe access along the tunnel, and the existing GRP lining in the designated section will be removed. Grout and concrete will then be broken out, followed by the construction of a new reinforced concrete lining to strengthen the structure.
Barhale Regional Manager Florin Edu stated that these works will ensure the long-term resilience and reliability of this strategic asset, noting that the construction methodology was determined through collaboration with Thames Water during the ECI phase. The works will be carefully managed to ensure that a minimum flow from other WLA reservoirs is maintained into the treatment works, thereby sustaining the treatment process and preventing deterioration of the treatment beds.
The Ashford Common WTW is one of four treatment works supplied by WLA reservoirs, serving London via the Thames Water Ring Main (TWRM) network. Barhale has previously completed a repair at the Ashford Common North tunnel, also identified during a routine inspection, with a full lining replacement for that section planned for a future project. Additionally, last month Thames Water awarded Barhale a £12.5 million contract for statutory tunnel inspections and maintenance across multiple assets under the AMP8 Tunnels & Aqueducts program. This includes raw water assets within the Thames Water Ring Main, the London Northern Abstraction area, and the New River region, as well as production tunnels at other Thames Water treatment works. As part of this program, nearly 48 kilometers of tunnels are expected to be inspected.
