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HEX collapse report slates poor risk management

A CATALOGUE of design and management errors, poor workmanship and quality control were at the root of the catastrophic tunnel collapse at London's Heathrow Airport in 1994.

So says the Health & Safety Executive in its final report on the 1994 Heathrow Express collapse, described as 'the worst civil engineering disaster in the UK in the last quarter century'.

The report is the result of years of investigation by the HSE's specialist team and was published following the completion by of legal proceedings and largely guided by the case's outcome.

Investigators found the incident exhibited 'all the hallmarks of an organisational accident'.

'The collapses could have been prevented but a cultural mindset focused attention on the apparent economies and the need for production rather than the particular risks, ' it says.

'Warnings of the approaching collapse were present from an early stage in construction but these were not recognised.'

Errors were made, it says, 'leading to poor design and planning, a lack of quality during construction, a lack of engineering control and most importantly a lack of safety management.'

The tunnels collapsed in the early hours of Friday 21 October 1994 and continued to fail over a number of days. The failure brought chaos to the heart of Heathrow Airport Although no one was killed or injured in the accident, HSE says the incident was 'one of the worst civil engineering disasters of the last quarter of a century'.

Recovery took nearly two years and cost around ú150M ($226M) - nearly three times the cost of the original contract.

Other projects using sprayed concrete tunnelling methods in the UK including the Jubilee Line Extension and the Heathrow Airport baggage tunnel were suspended and delayed.

Balfour Beatty and its tunnel designer Geoconsult were subsequently fined a total of ú1.7M - a record at the time for offences under Health & Safety legislation.

'Such accidents must be prevented through effective risk management. The industry cannot simply rely on good fortune, ' says the report. 'Risk assessment should be a fundamental step in the procedures adopted by all parties: it is inappropriate wholly to leave the control of risk to contractors.'

The report highlights the risk of safety dependent activities being influenced by contractual relationships. 'Cases in point may be new forms of contract where roles are poorly understood and new technologies where people variously rely on others to understand, communicate and control the risks.'

To overcome this, the report says: 'those involved in projects with the potential for major accidents should ensure they have in place the culture, commitment, competence and health and safety management systems to secure the effective control of risk and the safe conclusion of the work.'

According to the HSE, the direct cause of the tunnel collapse was a chain of events. This included a myriad of unchecked substandard construction over a period of some three months, grout jacking that damaged the tunnel plus inadequately executed repairs some two months before the collapse.

The construction of a parallel tunnels in failing ground led to a major structural failure and progressive failure in the adjacent ground during October 1994.

The collapse of NATM tunnels at Heathrow Airport , published by HSE Books, tel: (01787) 881165, or www.hse.gov.uk

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