The northern outfall sewer (NOS) at Manor Road, West Ham, is a a 7.5km-long wastewater pipeline running across East London transferring flows from a 300km3 catchment to Beckton Sewage Treatment Works.
It passes above the Jubilee Line, Dockland Light Railway and Manor Road.
The NOS is made up of five separate parallel sewer ‘barrels’. Three were originally constructed by Sir Joseph Bazalgette between 1860 and 1865; the other two were added around 60 years later. Each of the sewer barrels is 2.7m in diameter.
Works are constrained by the need to maintain flows through the sewer throughout the programme and to minimise disruption to train travel.
Waste water passes through the pipes at a combined rate of more than 22,000 litres per second, meaning that over-pumping is not feasible.
Instead, Barhale will employ a series of carefully-phased isolations with no more than two sewers taken out of service at any one time.
Once the sewers are isolated, 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 plans to use stainless steel pipework fabricated offsite to remove the need for on-site welding and ensure the high levels of quality and precision required.
The contractor will also survey 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 for the southern region, said: “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.
“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 is expected to extend the life of the sewer for another 120 years. Completion is expected in summer 2027.
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