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Behind the scenes of Crossrail's tunnel digging

By Time Out London contributor
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Miles of tunnels have been dug beneath London’s streets for Crossrail’s trains. As the last few tons of earth are excavated, Andy Hill finds out where they’ve been putting it.

Tunnels - you either dig them, like I do, or they’re boring. For the past three years, eight monstrous machines have been eating their way through the earth beneath our city, tearing London a new one for Crossrail: the largest civil engineering project in Europe. Now, they’ve only 750 metres left to travel before the tunnels are complete. You’re probably familiar with the noise, the hoardings and the travel disruption. But have you ever wondered what they do with all that excavated dirt? Well I have, and so I went to find out.

If you were thinking engineers could just discreetly shake it out of their trouser legs at ground level, a la Tim Robbins in ‘The Shawshank Redemption’, I’m afraid…nope. There’s around 4.5 million tonnes of the stuff - that’s more than 2,000 London Eyes - so even if MC Hammer helped out with his most voluminous harem pants, it wouldn’t get shifted any time this century.

So where does it end up? The answer is Essex. Thanks to a unique partnership with feathered friend-savers the RSPB, the soil is being carted to an island in the Thames Estuary to form abrand-new nature reserve. The plan is to beat climate change by raising disused farmland on Wallasea Island by several metres, thus saving some of the UK’s most precious wildlife. We’re not talking one-legged pigeons here. The reserve will be home to kestrels, owls and peregrine falcons; to seals, adders and newts. Best of all, from July you’ll be able to go and pay them a visit.

RSPB Seal

I’m a massive nature buff, and a train nerd, so following the excavated soil along its route from scary metropolitan construction site to bucolic islet is right up my street. And getting to meet the legions of hardworking Londoners turning grit into an avian heaven is a bonus.

Still, my introduction to Crossrail is rather more brutal than this idealised vision. ‘Are you afraid of heights? Well, it’s a bit late now.’ With that, I’m shoved on to an offputting temporary staircase and marched down a dizzying 45-metre shaft below Finsbury Circus by site manager and authentic gruff Irishman John Rodgers. A veteran of epic boring projects such as the Channel Tunnel and the Athens Metro, this man, it’s safe to say, knows his holes.

‘See this here?’ he says, emphatically stomping his boot in the wet mud when we hit the bottom. ‘Virgin land. Not a soul trod here till we did.’ He leads me across the rough concrete-lined chamber that will eventually become Liverpool Street station’s new ticket hall, and introduces me to ‘Elizabeth’, one of eight Crossrail tunnelling machines. I’m struck dumb by her vastness. Seven metres high and 150 metres long, she weighs more than a thousand tonnes, and requires 20 men working flat out to keep her hellish steel incisors carving out the cathedral-like catacombs I’m standing in now.

I do have one worrying question, though. How come, with all that terra firma being gnawed away, the buildings above ground don’t collapse? Turns out it’s okay if they do, a bit: ‘We’re technically allowed to let the ground above the tunnel sink by 2 percent.’ Gulp. To this John proudly adds: ‘So far we’ve kept to less than half that. You’d never know above ground.’ Touch wood, eh?

The earth is transferred, via Elizabeth’s churning metal guts, to a fleet of tipper trucks that take it to Barking for processing. Sandwiched between a grisly industrial estate and an unaccountably pretty bend in the river Thames, the Barking site handles up to 200 trucks a day, all piled high with tunnel-fresh soil. This is refined to the standard newts insist upon, then the precious, grubby cargo (which I’m becoming quite attached to by now) is loaded on to barges and carried on the 11-hour last leg of its journey to Wallasea Island.

A fine mist is settling as we drive on to the island. James Preston, my ride, set up the Barking operation, and takes pride in the fact that his brainchild has to date processed more than 1.7 million tonnes of what he calls ‘the material’. Before we arrive at the southern portion of island, where the soil is headed, I spy a large field separated from the rest by plastic fencing. ‘That’s where we stashed the animals before getting works under way,’ says James. ‘We had to manually transfer 8,200 lizards, 150 water voles, 30 snakes and an entire badger sett.’ It occurs to me that it’s a rare and wonderful thing to meet a guy in a hard hat and steel-toed boots rhapsodising about the tender transportation of a newt, rather than, say, tipping a bucket of cement over it.

As we approach ground zero I can make out the eerie, dinosaur-like profiles of a fleet of diggers perched on the sea wall, terraforming ancient farmland into a haven for wetland creatures. Parking up at the dockside, we’re fortunate enough to catch a barge unloading its cargo of Zone 1 subsoil - one of the last ever, my guide tells me with a touching hint of emotion.

Bird

This summer, once all the earth is on site and arranged to the RSPB’s exacting specifications, the sea walls will be breached, allowing the North Sea to flood in and form salt marshes around a custom-designed archipelago perfect for wading birds and fish seeking a discreet place in which to lay their eggs. It’s amazing, pioneering stuff, executed on a monumental scale, and worth bearing in mind the next time you’re in a huff about not being able to get on the Central line at Tottenham Court Road.

I’ve a newfound respect for the grubby stuff beneath out feet. It’s a valuable resource, and although all the borers, the diggers, the barges and the badger-relocating might seem like an awful lot of trouble to go to, this is a really positive fringe benefit from Crossrail.

As we head back to the mainland – James’s Land Rover now packed with site workers - the chit-chat pauses for a moment as an egret takes flight up ahead of us. ‘All this is for them,’ muses someone in the back, with an unmistakable air of wonder. ‘You’ve gotta love an Essex bird, eh?’

GLORIOUS MUD!

How Crossrail’s dirty business piles up

55 million How many years London’s clay had remained undisturbed, before Crossrail’s boring machines got stuck in.

100 metres a week The not-quite-Usain Bolt-level top speed of the drills.

25 Miles of train tunnels already dug.

10,000 Crossrail employees – working across 40 construction sites. 62 million Man hours they’ve already put in.

250 How many metres long the new Crossrail platforms will be. That’s nearly as long as the Shard is tall!

2,400 Bargeloads of earth delivered from the London tunnels to Wallasea Island in Essex. 670 Hectares of farmland transformed by the incoming soil: an area about 2.5 times larger than the City of London, but with 0.0 bankers (thankfully).

By Andy Hill

Want to read more about Crossrail? Check these out:

Video: see the Crossrail tunnels underneath the Barbican

Crossrail workers discover 5,000 human remains in burial ground in Liverpool Street

‘Crossrail for bikes’ is happening (and building starts next month!)

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