Barhale has been appointed by Thames Water to deliver a £12.5m tunnel inspection and maintenance programme across key water infrastructure in London.
The statutory programme covers assets including the Thames Water Ring Main and North London Abstraction and New River Zone raw water infrastructure.
Barhale tunnel inspection programme covers key Thames Water assets
The projects have been awarded under Thames Water’s AMP8 Tunnels and Aqueducts programme.
The work includes production tunnels within Thames Water’s treatment works, bringing the total length of tunnels under inspection to almost 48 kilometres.
On the Thames Water Ring Main, Barhale will use mainly man-entry inspections, with limited use of remotely operated vehicles where appropriate.
Inspections planned across Ring Main and Lee Valley assets
Barhale will inspect 12 sections of the Thames Water Ring Main at depths of up to 65 metres. These sections represent around 20% of the asset’s extent.
At the North London Abstraction and New River Zone, the company will carry out 24 inspections around the Lee Valley reservoir complex.
The tunnels in this area vary in diameter, are buried up to 50 metres deep and range from 30 metres to 5,450 metres in length. The overall length to be inspected in the Lee Valley area is 24.9 kilometres.
ROV, CCTV and sonar surveys to support confined space work
Where in-person inspection is not possible, Barhale will use remotely operated vehicles, CCTV and sonar surveys.
The tunnels will be accessed from existing shafts. Works will take place under confined space working conditions and will include clearing sludge, silt, stones and invasive species, particularly mussel concentrations that can affect flows.
Barhale estimates that 3,120 tonnes of waste will be removed during the programme.
Maintenance works include repairs and valve replacement
Barhale will carry out minor repairs including mortar repairs, leak sealing and resin injection.
The company will also replace or repair access furniture such as ladders, landing platforms and covers.
Specialist diving teams will complete repairs to inlet screens and eel screens, and carry out external shaft repairs. Major repair requirements will be identified and taken forward for appropriate action.
The programme will also include replacement of nine large-diameter valves.
Environmental protections planned around Lee Valley sites
Several Lee Valley projects are located in Sites of Special Scientific Interest and Ramsar-designated areas. Walthamstow Wetlands is a conservation area open to the public and forms part of the wider Lee Valley ecological landscape.
London Wildlife Trust describes Walthamstow Wetlands as an internationally important nature reserve, while its bird information states that the site is a Site of Special Scientific Interest and part of a Ramsar wetland.
Barhale said work is planned to protect existing bat and newt populations in the tunnels.
Barhale highlights confined space safety
Steve Best, Senior Project Manager at Barhale, said: “This programme involves complex work in confined spaces and live water environments. We have developed inspection and isolation processes with Thames Water over more than 20 years, and they are designed to keep our teams safe while maintaining reliable operation of the network.
“We are proud of our safety record and continue to improve how we manage risk through the introduction of a new confined space working training regime. It imposes new site entry controls and will see all operatives qualified to the highest level.
“Our double isolation protocol, developed with Thames Water, also ensures that there is an additional layer of protection for teams working near live tunnel sections.”
The final inspections will be conducted by Thames Water Reservoir Engineering teams.
For more updates on water infrastructure and asset maintenance, visit the H2O Global News Water Management section.
