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Benefits of hindsight

Making mistakes is fine so long as you learn from them. Sounds sensible but in construction it is amazing how often this truth is ignored or forgotten.

The Channel Tunnel Rail Link team is determined not to let this happen. On contracts 350 and 410 past experience of building sprayed concrete tunnels and of incrementally launched viaducts has been scrutinised and proposed construction methods altered accordingly.

The collapse of the Heathrow Express tunnels in 1994 woke up the world of shotcrete lining. The CTRL team has since studied all the available information, including the text of Justice Cresswell's damning courtroom conclusions following February's successful three week prosecution of Balfour Beatty and Geoconsult for their role in the disaster.

Clearly there are differences between the two projects, most obviously that the 14.2m wide CTRL tunnel passes through relatively stable chalk ground rather than London Clay. But the introduction of robotic spraying nozzles, the use of daily ground movement reports and review meetings, plus rigorous inspection and testing regimes, are all direct reactions to the HEX collapse.

The CTRL contract stipulates self certification - and for sprayed concrete structures in the wake of HEX this has to be approached correctly.

'Most of the UK-based guys on site are used to self certification,' says Eurolink's Andy Sindle. 'We carry out independent checks - senior engineers acting independently from the tunnel construction management.'

The most significant move, however, is the appointment of Alan Myers to manage the contract for Union Rail. The former Balfour Beatty HEX project director is perfectly placed to learn and act on the lessons of the past.

He is working alongside Sindle, and the direct experience gained from an incident on the scale of HEX means that between the two of them there should be few surprises.

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