The Northern Outfall Sewer is a major gravity sewer which runs from Wick Lane in Hackney, along The Greenway to Beckton sewage treatment works in east London. Most of it was designed by Joseph Bazalgette after an outbreak of cholera in 1853 and the "Great Stink" of 1858. The creation of the NOS was a massive undertaking, and involved the construction of huge embankments and several bridges, one of which is Waterworks Bridge.
The bridge, which passes over Waterworks River, comprises of two spans of reinforced concrete, and one of wrought and cast iron, each span is around 14m and all have seen better days. Four huge brick-built sewers approach the bridge from the east, before dividing into six sewer barrels at the bridge, and splitting again into eight as they leave the bridge on the north side. Why the pipes were divided on Waterworks Bridge, no one really knows, but it certainly makes replacing them an interesting task.
“We can only close off one sewer at a time,” says John Mckay, eight2O’s construction manager, “as at peak flow the system carries 32,000 litres per second – that would fill an Olympic sized pool in just over a minute!
“So, we’re building a temporary support structure above and below the bridge to, effectively, sandwich the old sewer barrels while we carry out the work. We’ll then work on replacing one barrel at a time with a new insitu cast concrete one. To do this we need to isolate each barrel as we go and remove the bridge and decking in sections.
“It sounds a straightforward job but, trust me, this is very delicate work and each sewer barrel has some dependency on the barrel next to it – we can’t afford any mistakes.”
Besides being a complex replacement, the Waterworks Bridge project team are also replacing a 20 inch water main on the side of the bridge, as well as removing an old asbestos sludge main, two unused high voltage cables and working around a number of fibre optic cables inside the sewer.
Work at Waterworks Bridge began July 2017 and is expected to complete by January 2019 Once the barrel replacements are complete, the bridge decking will be replaced, new ‘over slabs’ will be laid to allow 7.5 tonne vehicles to use the bridge, and all the street furniture will be replaced.
Eight2o, via Costains compound,
Bridgewater Road Bridge, off Warton Road.
|Length of Visit||2 Hours|
|Maximum Group Size||20|
|Register by||March 19, 2018|
The next Open Doors will take place in 2019.