Inside the huge London super sewer designed to fight river pollution

Inside the huge London super sewer designed to fight river pollution

In simply over a 12 months’s time, the place I’m standing will probably be pitch black, devoid of human life and – on a nasty day – stuffed with human effluent. I’m in London’s new tremendous sewer, a monstrous concrete pipe that runs roughly alongside the course of the river Thames for 25 kilometres. It’s designed to unravel an issue that London and plenty of different cities have been grappling with for many years: the discharge of uncooked sewage into rivers.

London’s present sewage system is creaking on the seams. It was constructed between 1859 and 1875 after the Nice Stink of 1858. On the time, town’s inhabitants was round 3 million. The visionary engineer Joseph Bazalgette designed a sewer to deal with 4.5 million folks plus rainwater. Round 9 million now use it, the climate is wetter and London has been extensively concreted over, stopping rainwater from being absorbed by the bottom.

The system can not cope. Round 60 occasions a 12 months it overflows, dumping a complete of 40 million tonnes of uncooked sewage per 12 months into the Thames plus moist wipes, sanitary merchandise, condoms and no matter else folks see match to flush down the toilet.

“Our job is to construct a sewer that can tackle that,” says Andy Mitchell, CEO of Tideway, the corporate behind the mission. The reply they got here up with was to construct a huge overflow pipe deep underground, beneath the Victorian sewer, to intercept its overflows. The Tideway Tunnel is one of many greatest metropolis sewer initiatives on the earth, says Mitchell.

It received’t resolve the issue utterly: when the rain is basically heavy there’ll nonetheless be discharges. However it’s going to scale back their frequency to round three of 4 occasions a 12 months, and the overflow will probably be predominantly rainwater. “The Bazalgette system will get stuffed with undiluted sewage,” says Mitchell. “If it rains closely, that will get channelled into the sewers, and the sewers get full. They then flush into the river. However it’s that first flush, which is pure sewage, which is essentially the most damaging. We seize that.”

We package ourselves out in high-vis clothes, exhausting hats and boots and head to the entry shaft, a yawning concrete caldera concerning the diameter of a cooling tower and 50 metres deep. It must be this massive to get the massive boring machines all the way down to the place they do their boring stuff.

We clamber into the “VIP carry” – really a steel cage connected to a crane – and are gently lowered to the underside. From there we stroll down the sewer itself to get a really feel for the dimensions of this colossal engineering mission. The round tunnel is 7.2 metres throughout. It took eight years to construct at a value of £4.5 billion. Its whole capability is 1.6 million cubic metres.

There isn’t any sewage in there now – the soiled work begins subsequent 12 months – and the tunnel is eerily lovely, like easy alabaster within the chilly glow of the strip lights. “This is without doubt one of the most photogenic items of tunnel I’ve ever constructed,” says Mitchell. That’s as a result of there’s a sinuous kink that’s oddly pleasing to the attention. It wasn’t deliberate however they needed to skirt round a boring machine that grew to become caught, doing a “flip and bury” manoeuvre to get it out of the way in which. The borer is now sealed behind the concrete tunnel wall and will probably be there without end.

The tunnel slopes gently down from west to east, a couple of millimetres each metre. That allows the sewage to circulate by gravity, no pumping required. “It doesn’t sound a lot however it’s sufficient to maintain it transferring,” says Mitchell.

This descent provides as much as 55 metres alongside the size of the tunnel. When the sewage arrives at its vacation spot, Beckton Sewage Remedy Works, it’s 80 metres underground and must be pumped again up. However the tunnel itself has no transferring elements.

In round a 12 months, the mission will probably be full. The lights will probably be eliminated, the entry shafts capped and the tunnel plunged into lonely darkness for no less than 120 years. It’s attainable that we’re among the many final folks to set foot in it, says Mitchell. Upkeep inspections will probably be carried out by drone. “Technically we may go down if we have now to,” he says. “However except there’s a restore, which is extremely unlikely, we’re unlikely to ever go down there once more.”


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