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Engineers investigate new collapse

ENGINEERS investigating the cause of a massive hole that appeared above tunnelling work on the £5.2 billion Channel Tunnel Rail Link are looking at a possible link with a crater that appeared nearby five days earlier.

Investigators from the CTRL project team and the Health and Safety Executive are studying ground monitoring data and records from the tunnel boring machine's 'black box' recorder to establish why a 10 m-diameter hole appeared in back gardens in Stratford, east London on Saturday night.

Work on the £120 million Costain/ Skanska/Bachy CTRL contract 240 to drill a 4.7 km-long, twin-bore, 8.1m-diameter tunnel between Stratford Station and Barrington Road has been stopped until the cause of the collapse is known.

Thirty-five local residents were also evacuated to hotels while the area of subsidence in the gardens was filled with 250 cu m of concrete.

The earth pressure balance tunnel boring machine drilling the tunnel passed under the gardens about 36 hours prior to the collapse. It is now 'parked up' 30 m along the route.

A spokesman for project manager Rail Link Engineering said: 'Investigations into the cause of the subsidence are continuing, but it is believed that it may be associated with one or possibly two redundant water wells constructed in the 1860s which may have been intersected by the tunnel.'

A Newham Borough Council spokeswoman insisted the tunnellers should have known about the wells. She said: 'We told them all about the wells - they're common knowledge with locals.

We're digging out the details.'

The team was already investigating an incident five days earlier involving an articulated lorry reversing into a hole that suddenly appeared in nearby Grove Crescent Road.

There was speculation the collapse had been caused by a sewer as the TBM had passed under the site eight days earlier.

Investigators are now examining whether the incidents are linked.