Barhale has been contracted by Thames Water to remediate the mains on a critical section of the East London sewer network and replace a discharge chamber with a prefabricated alternative.
The £7.8M programme is unfolding in Barking, east London, where 800mm diameter twin rising mains run from the Store Road Pumping Station, north of the Woolwich ferry terminal, to an outfall that discharges into the Northern Outfall Sewer (NOS) near the Beckton Sewage Treatment Works inlet.
Barhale’s work entails the rehabilitation of the two sections of parallel rising mains dating back to the 1970s. One section will require Barhale to replace the existing sewer with two lengths of 142m, 800mm diameter HDPE pipe – flexible plastic piping used for the transfer fluids and gases – to be installed through open cut excavation.
For the other section, Barhale will repair a 220m length of each main using Cured in Place Pipe (CIPP) relining. CIPP entails inserting a flexible liner inside an existing pipe, inflating the liner, and exposing it to heat or ultraviolet light to harden it inside the pipe.
A temporary rider system will be installed to isolate the works and allow flows to be maintained.
Barhale water director – southern region – Shane Gorman said the sections of the mains dated back to 1977 and had come under increased pressure from development in the area.
Gorman added that, “alongside the rehabilitation work, we will also be conducting detailed CCTV surveying of a further 31m of the elevated bridge structure that discharges into the NOS to ensure that it is in satisfactory condition.”
Once the pipeline work is completed, a prefabricated Glass-reinforced plastic (GRP) discharge chamber will be installed.
Gorman said: “We have moved away from a traditional concrete discharge chamber and instead will be demolishing the existing chamber to install a modular GRP unit.”
He explained that the chamber design needed to take into consideration high levels of hydrogen sulphide and weight restrictions on the NOS. The new unit is also lighter and more durable than its predecessor, as well as being manufactured using low carbon methods. It will also reduce installation time on site.
Thames Water announced in January 2023 that NOS itself would be upgraded, entailing a £70M investment over three years to ensure its pipes would remain resilient for generations.
Commenting at the time, Thames Water project manager Richard Smith said: “As custodians of this incredible infrastructure we need to ensure our pipes are resilient to the pressures of climate change and population growth and we can continue to provide reliable services to our customers. This upgrade to our network will help protect customers and the health of the River Thames.
“The Northern Outfall Sewer supplies Europe’s largest sewage works at Beckton, which treats the waste of more than 4M Londoners, so we need to make sure the pipes continue providing this vital service for at least another 100 years.”
Most of the NOS was designed by Joseph Bazalgette, following an outbreak of cholera in 1853 and the Great Stink of 1858, which saw hot weather intensify the smell of untreated human waste and industrial effluent on the banks of the Thames.
The Victorian pipes were originally constructed between 1860 – 1865 and each sewer is 2.7m in diameter – large enough to drive a transit van through. Wastewater flows through the pipes at a rate of up to 20,000 litres/s, which could fill an Olympic size swimming pool in two minutes.
Meanwhile, Beckton Sewage Works forms a key part of London’s £4bn new super-sewer, the Thames Tideway Tunnel, scheduled to open in 2025.
Photo: diamond geezer, via Flickr
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