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HEX tunnel dogged by errors - HSE

A CATALOGUE of design and management errors, poor workmanship and quality control were at the root of the catastrophic tunnel collapse at 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 focussed 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 150M - 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 1.7M - 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

What they said about the report

Kevin Myers HM chief inspector of construction ‘Most lessons are relatively straightforward. Put at its simplest, the incident could have been prevented if proper consideration had been given to identifying the hazards and consequences, and to controlling the risks. It must never be forgotten that construction work can result in major accidents which put workers and the public at risk.

The means of preventing them are clear. The report provides the opportunity for action. Those involved in the industry must take account of the wider lessons.’

Sir Alan Muir Wood Independent member of the HSE investigation team. ‘The lessons for the industry are to look much further than the operational failures highlighted in the report and ask why does this situation occur. It is actually a process of relearning what we already know. There is a lot that has been discussed (in the wake of the collapse) about the process of construction and not enough about the procurement. We have to recognise that construction is all about combining the management and the engineering together.’

Andy Rose Balfour Beatty managing director ‘We will never try to change our plea of guilty but it is clear that the collapse was the result of organisational blindness. There was much honest endeavor on the project and it is fair to say that we have come a long way since then and are fitter and better having had the experience from the lessons learned. The collapse is a landmark in the industry and a reminder to all those operating in the industry. While the report highlights some good lessons, its basis is from an adversarial legal process and it is unfortunate that there does not seem to be an alternative means of uncovering the truth.

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