Public, workers, exposed to serious risk in 1994 tunnel collapse
The public and those involved in construction work at the Central Terminal Area (CTA) of Heathrow Airport were exposed to serious risk of injury, concludes a report published by the UK Health and Safety Executive (HSE).
The collapse of the tunnels, during the night of Oct. 20, 1994, was one of the worst civil engineering disasters in the UK. Although no one was injured or killed, the collapses continued over a number of days and led to disruption at Heathrow Airport and delayed the Heathrow Express Rail Link project. The project used the New Austrian Tunneling Method (NATM) and it was the first time that construction method was used on London clay.
"The report points out that although there were human errors, these were a consequence of foreseeable organizational failures," commented Kevin Myers, HSE's chief inspector of Construction. "The collapses could have been prevented but for a cultural mind-set which focused attention on the apparent economies and the need for production rather than the particular risks."
He added that other warnings of the approaching collapse, which were present from an early stage in the construction, went unrecognized. "There were also no effective arrangements for involving workers or for seeking their views on health and safety matters," Myers concluded.
HSE's investigation found that the direct cause of the collapse was a chain of events involving:
- Substandard construction in the initial length of the CTA concourse tunnel over a period of three months.
- Grout jacking that damaged the same length of tunnel plus inadequate repairs to it two months before the collapse.
- The construction of a parallel tunnel in failing ground.
- Major structural failure in the tunnels, progressive failure in the adjacent ground, and further badly executed repairs during October 1994.
HSE brought legal proceedings against Balfour Beatty Civil Engineering, the principal contractor, and Geoconsult ZT GMBH of Austria, their expert advisers, alleging breaches of sections 2(1) and 3(1) of the Health and Safety at Work Act of 1974 at the CTA and also Terminal 4 (T4). Balfour Beatty pleaded guilty to the CTA offenses and was fined GBP 1.2 million, a record at that time. HSE decided not to proceed on any of the T4 matters in the light of the CTA guilty pleas by Balfour Beatty Civil Engineering.
Following a trial, Geoconsult ZT GMBH of Austria were found guilty of the CTA offenses and fined GBP 0.5 million. Geoconsult failed in an appeal against conviction and sentence. They have since lodged a complaint with the European Court of Human Rights.
"Those involved in the construction industry must learn the wider lessons from this incident and put health and safety at the center of all projects," said Myers. Those key lessons are:
- Recognize and address the potential for major accidents -- particularly in projects with potentially aggravating factors such as those involving new or unfamiliar technologies or close proximity to the public.
- Build a business culture in which health and safety is paramount.
- Put effective risk management at the core of robust health and safety systems.
- Ensure that the key players -- clients, designers, contractors and workers -- co-operate and work well together to secure the highest standards.
Copies of The collapse of "NATM tunnels at Heathrow Airport" (ISBN 0 7176 1792 0, price GBP13.50) can be ordered online at www.hsebooks.co.uk or are available from HSE Books, PO Box 1999, Sudbury, Suffolk, CO10 2WA.
Edited by Sandy Smith