Thames Water has appointed Barhale to deliver essential remediation works on the Northern Outfall Sewer (NOS) - a 7.5 kilometre-long wastewater asset running across East London that transfers flows from a 300 square kilometre catchment to Beckton Sewage Treatment Works.

An innovative £36 million relining will remediate an essential gravity sewer as it passes above the Jubilee Line, Docklands Light Railway and Manor Road in West Ham, East London.

The sewer is made up of five separate, parallel sewer barrels: Three were originally constructed by Sir Joseph Bazalgette between 1860 – 1865 and then another two were added around sixty years later. Each existing sewer barrel is 2.7metres in diameter.

Works are constrained by the need to maintain flows through the sewer throughout the programme and to minimise disruption to train travel. Wastewater passes through the pipes at a combined rate of more than 22,000 litres per second – meaning that overpumping is not feasible. Instead, a series of carefully phased isolations will make the works possible. No more than two sewers will be taken out of service at any one time, keeping at least three live at all times.

Once isolated, civil engineering and infrastructure specialist Barhale will strengthen the existing structure with a specially-designed Duplex Stainless Steel pipes.

Barhale’s Senior Contracts Manager Jaimie Lawson explained that the company is working closely with Thames Water to develop a phased approach.

“We are shaping the programme to allow sewer flows to continue throughout the works while avoiding rail possessions and disruptions to road traffic,” he said. “Although the NOS is an essential part of London’s water infrastructure, it is probably less well known that it also forms the bed for the popular Greenway footpath and we want to make sure that we minimise any impacts on the community.”

Barhale is working with Thames Water to conduct the design and build project. The new steel pipework for the project has required sourcing from Barhale’s supply chain within the UK for fabrication and materials from suppliers in the EU. Offsite manufacturing of the stainless-steel elements will remove the need for on-site welding and ensure the high levels of quality and precision required are achieved.

Barhale will also facilitate surveying of the condition of the cast iron pipe and hangers that suspend the sewers over Manor Road prior to replacement or refurbishment.

Shane Gorman, Barhale’s Water Director – Southern Region, underlined the strategic importance of the works.

“The Northern Outfall Sewer provides a critical flow across the capital and ensuring it is able to continue to serve the communities of North East London is essential,” he said.

“We are very pleased to be working alongside Thames Water to deliver this important piece of work, connecting to the Thames Tideway Tunnel and contributing to the overall update of the capital’s water infrastructure.”

The project will increase the design life of the asset for another 120 years. Completion is expected in summer 2027.