The treatment works is fed by the reservoirs which form part of the West London Abstraction area. Mandatory five-year inspections carried out by Barhale鈥檚 Tunnels & Aqueducts team identified inconsistencies in the Southern Inlet tunnel鈥檚 existing glass reinforced plastic liner. They presented a risk of damage to the underlying wedgeblock tunnel. Under the new contract, Barhale will reline the affected section, safeguarding London鈥檚 drinking water supply.
The award follows completion of an Early Contractor Involvement (ECI) phase. Barhale worked closely with Thames Water to finalise designs and address the access constraints presented by the congested underground infrastructure of layered tunnels.
Work will begin with excavation to a depth of 3m to expose the chimney and riser for initial access.
Segments of the riser will then be demolished to allow safe descent to the 19.5m tunnel invert level. From there, scaffolding will be installed to enable access along the tunnel, allowing the team to remove the GRP liner.
Once this is complete, they will break out the grout and concrete and construct a new reinforced concrete liner to restore long-term structural integrity.
Barhale has previously completed a local repair in the Northern tunnel at Ashford Common WTW, which was identified during routine proactive inspections. Full relining of the section is earmarked for a later project.