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HEX collapse case told of '50mm tunnel linings'

SELF CERTIFICATION systems on the Heathrow Express project were not understood and led to tunnel linings being too thin, the HEX trial was told this week.

BAA area manager Jonathan Allen, the most senior member of the client's HEX team to give evidence at the trial, said: 'I saw shotcrete in the construction of the invert [under Cambourne House] with a total thickness of around 50mm. The invert in this area should have been around 300mm.'

He added that BAA had raised concerns with main contractor Balfour Beatty over the quality of work and site supervision, and criticised Balfour Beatty's attitude to the tunnels' unique Contractor Self Certification Scheme, developed by client BAA for the project.

'I felt Balfour Beatty were paying lip service to CSCS, and did not go sufficiently far to ensure systems required were in place,' he said in his written statement.

The Health & Safety Executive is prosecuting main contractor Balfour Beatty and its Austrian tunnelling expert Geoconsult under the Health and Safety at Work Act after the collapse of New Austrian Tunnelling Method tunnels on BAA's HEX rail link in October 1994. It alleges that both failed to ensure the safety of workers and the public during construction.

Balfour Beatty pleaded guilty to the charges at the start of the trial last week. Geoconsult pleaded not guilty.

Allen's comments came in a written statement read to the court by the prosecution counsel Hugh Carlisle QC. The prosecution has been taking evidence from tunnellers, engineers and management from the project to support its claims that there was poor quality and supervision on site. It was Geoconsult's responsibility, the HSE argues, to monitor quality control during construction.

'I was concerned with the lack of understanding in the HEX team and Balfour Beatty over CSCS,' said Allen. 'The misunderstanding was that Balfour Beatty felt HEX should not be involved. It was because of inconsistencies within HEX [in its approach to CSCS] that Balfour Beatty was able to exploit chinks within the system.'

The court was also told this week that the site investigation which provided geological information for the Heathrow Express project should not have been used as the basis for tunnelling work.

The claim was made in a WS Atkins report into consultant Mott MacDonald's site investigation. It was produced by defence barrister Arthur Marriott QC as he cross-examined the Health & Safety Executive's geology expert Professor John Hutchinson of Imperial College.

Marriott and his client Geoconsult surprised the court by appearing at the start of the week, having failed to offer a defence during the first week of the trial. However, on Monday Marriott confirmed that he would be attending for the rest of the case.

Under cross-examination by Marriott, Hutchinson said: 'I regard the site investigation being discussed here as a preliminary investigation.'

He added: 'It would surprise me if a tunnelling expert did not carry out a further investigation.'

The trial continues.

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