Heathrow Tunnel Collapse 1994 - Case Study Example

Heathrow Tunnel Collapse 1994 Table of Contents 1. Introduction - 3 2. Analysis of the Accident - 3 3. Consequences of the Accident - 7 4. Lessons Learned from the Accident - 8 5. Assessment of the Implications if such accident happen in Preston - 9 6. Conclusion - 9 7. Bibliography - 11 1. Introduction In 1994, a new underground railway tunnel and station were under construction beneath the Central Terminal Are of London’s Heathrow airport. During October, a section of the station collapsed and this led to the partial collapse of a building above it. Further collapses occurred during the next few days but fortunately, no one was injured. The purpose of this report is to investigate and conduct an analysis of this accident and find out the consequences and lessons learned from it. Moreover, the report would assess the implications of such accident if it would happen to Preston. Finally, it would a brief conclusion of the findings. 2. Analysis of the Accident The Heathrow Express project was conceived in 1986 as part of study to look at improving access links between Central London and Heathrow airport. The rail link runs on the existing British main line from Paddington to north of the M4 from where, there is 8 km of new alignment to service stations in the Central Terminal Area and at Terminal 4 or T4. The T4 station comprises of two platform tunnels with central concourse at one end. These are connected by a series of cross-passages and intersected by the North and South Ventilation tunnels at each end of the station. The larges project under construction during that time, Heathrow Express was due to commence operations in June 1998. BAA will be the sole operator of the service, working in conjunction with Railtrack, which owns the line between Paddington and the airport junction. The service will operate brand new rolling stock to cut the time from Central London to Heathrow to some 15 minutes and will include check-in facilities at Paddington. It is planned to offer an additional service from St. Pancras station to Heathrow in 1999. It is estimated by BAA that the opening of the Heathrow will remove around 1.1 million vehicle journeys a year to the airport. This will make a major contribution to the reduction of road traffic in the airport area, which attracts more than 16,000 train, bus and coach arrivals every day. The company aims to encourage 50% of its passengers to use public transport to travel to and from the airport (Cole 2003, p.236). Prior to the collapse of the Central Terminal or CTA station tunnels, the Contractor, Balfour Beatty or BBCEL, with Geoconsult as designed, was responsible for the primary support, while Mott MacDonald or MM was responsible for the permanent support systems and each design section was independently checked by Faber Maunsell (British Tunnelling Society 2004, p.144). The tunnel is a £60m contract to build the main tunnels and stations for the Heathrow Express from Paddington to the airport. However, nine months into the work a major tunnelling collapse occurred. The total extra-unplanned cost has been reported at £422.7m or seven times the original tunnelling contract price (Blockley and Godfrey 2000, p.275) The tunnel was being constructed using a relatively new method known as the New Austrian Tunnelling Method or NATM, which had not previously been used in London clay. According to the Kletz (2001, p.61), the official reports says that in essence, BBA or the British Airports Authority decided that NATM works should be procured on a ‘design and construct’ basis rather than by the more traditional route whereby a client’s engineer develops a design and exercises supervisory oversight during construction. The chosen approach substantially transferred the process risks connected with the use of new technologies from the client to the contractor and this limited the opportunities for direct intervention by the client team. By assigning the choice and control of NATM to the contractor, BAA lost the ability directly to influence the work and to play an active part in the associated instrument-based monitoring regime. BAA chose to oversee the construction work indirectly through a system of infrequent audits and these proved ineffectual. BAA’s decision that they required staff competent in auditing rather than knowledgeable in tunnelling, further reduced their abilities to influence the work. BAA’s management systems failed to challenge the contractor sufficiently robustly on safety-critical issues. Unfortunately, the margin for error was small so that rigorous inspection during construction was necessary. In addition, the contractor’s workmanship was poor and when defects were noticed, the remediation was inadequate. Warnings of imminent collapse were not recognized, partly because of the inexperience of the people on the job. The Heathrow Express tunnel collapse was perhaps the biggest civil engineering disaster in the UK in the 1990s. The risks was enormous considering the works were tunnelling, traditionally a risky type of job in which risk are often shared because of the effect on progress of variable conditions. They involve the use of innovative tunnelling technology for the first time in the UK. By this method, level and internal dimensions of the tunnel are given to the contractor, the thickness of the tunnel lining and structure is effectively designed as the tunnel progresses, depending on the earth encountered and measured displacement around the tunnel. The works were under an area particularly sensitive to displacement. Heathrow is one of the word’s busiest international airports. The impact of a tunnelling risk occurring would be large (Broome 2002, p.48). During the early hours of October 21, 1994, three partly built station tunnels caved in and continued to collapse over a number of days. No one was injured or killed in the accident, but the failure, which was estimated to have cost Heathrow Airport operator BAA around 50 million. At about1:00 am on the morning of the collapse, ground-monitoring equipment measured movements ‘of the scale’ which alerted workers in the down-platform tunnel to the impending disaster. Twenty-five people were evacuated to the surface moments before the roof of the new station complex collapsed. It was discovered that the collapsed started at the based of the main shaft at the connections to the down-platform. With overburden material pouring into the fractured tunnel the semi-complete cavern was severely breached and the ground above swiftly sank (Bunni 2003, p.87). According the report, the problem was a weak tunnel invert. The contractor admitted that this was attributable to poor construction of the sprayed concrete lining. However, according to Bell (2004, p.230), the report of the Health and Safety Executive into the collapse of the Heathrow Express sited compaction grouting as a contributory cause of the collapse, in that it had damaged part of the tunnel lining that in turn had been inadequately repaired. At the trial, the subcontractor responsible for the monitoring was found to be guilty of failing to issue warnings when data from its monitoring instruments showed that collapses was imminent some weeks before the actual cave-in. In addition, they claimed that the readings were difficult to interpret and no one in any of the companies involved saw that there was a problem. There was also a controversy around the interpretations of the New Engineering Contract (NEC) that was used. Any OM project requires a close collaboration between design and construction because design continues through into the constructions process. The issue was whether this is possible under the NEC (Blockley and Godfrey 2000. p.275). However, the real hazards were the breakdowns in the process of OM. Roles were either allocated inappropriately or else were insufficiently understood by those taking them on. The critical nature of the need to monitor the ground as the work progressed was not appreciated. The contractor admitted that everyone was inexperienced at self-certification and the use of that phrase indicated an ambiguity of responsibility within the process. There was no clear understanding of success for the team. The responsibility for quality assurance was not as clear as it is should have been. As time pressures mounted the warning were not recognized and all of the factors combined to cause the collapse. The collapse of NATM tunnels at Heathrow airport was classified as an ‘organizational accident’ where errors were made leading to poor design and planning, a lack of quality during construction, a lack of engineering control and significantly, a lack of safety management (Villaescusa and Potvin 2004, p.452). 3. Consequences of the Accident “Becauee the tunnel infrastructure is so expensive it is inevitable that tunnel incidents can cause sever consequences” (Carvel and Beard 2005, p.422). The principal contractor was fined £1.2 million, at the time the largest single fine ever imposed for an offence under the Heath and Safety at Work Act, and a company providing expert advice to them was fined £500,000 (Kletz 2001, p.62). No one was injured but the incident was described in court as one of the biggest near misses in years. Fines and costs totalling £1.4 million were imposed on the two contractors held responsible. The associate costs of the disruptions to flights at a major international airport are massive (Bateman 2006, p.336). 4. Lessons Learned from the Accident There is a strong evidence to suggest that most project failures can be attributed to the impact of the people involved in the process. According to Lant and Shapira (2001, p.306), eighty percent of all project risks are human related. The accident provided an example of why it is essential to ensure that information available at the delivery end of any processes needs to be understood and fed back into our decision making process at a speed that reflects the reality of events. Most construction sires are provided with lots of instrumentation for settlement monitoring; however follow up action on these data remains an area of concern. In addition, in order to achieve targets sometime the management gives priority to faster progress and safety is neglected. What had happened during the construction of Heathrow tunnel in London where indications from monitoring instrumentation of consistent circumferential movement of tunnel lining coupled with depression of crown were overlooked during NATM construction. From these shortcomings, we learn that prompt action from the supervisor could avert the occurrence or the collapse of the tunnel (Kaushish and Ramamurthy 2000, p.502). Other collective lessons learned are that potential for major accidents must be recognized through use of hazard identification, consequences analysis and risk reduction strategies. New technologies need to be thoroughly understood and tested before being implemented. Finally, production pressure needs to be balanced by a defensive precautionary system. 5. Assessment of the Implications if this accident happen to Preston Preston is a progressive city with modern infrastructures in its grounds thus building a tunnel with the same project management technique used in Heathrow Express would entail enormous risks. The Heathrow Express tunnel accident is not a disaster caused by nature or technological failure, but an accident caused by sheer human error and negligence. The act of employing inexperienced contractors and staff will tell us that this project will fail from the very beginning. Hazards alone do not cause accidents and a number of studies suggest that a factors contributing to why accidents happen include poor decision-making and subsequent reaction to the situation. Lack of adequate and appropriate group management, supervision and organization. Lastly, the under-estimation of potential risk and hazard (Raymond 1999, p.29). Considering the lessons from the well-known Heathrow Tunnel accident, the leaders of Preston may have learned the consequences of organizational accident. However, given that such accident happened in Preston, then the impact would be greater and perhaps lives may be lost since it is a commercial and highly populated area. 6. Conclusion Conceived in 1986, the construction of the Heathrow Express tunnel started in 1994 but after nine months of work, a section of the station collapsed. Although no one was injured, the collapsed caused the partial collapsed of a building above the section. After the investigation, the collapsed of the tunnel was considered an organizational accident where mistakes during the design and planning were made. The lack of quality during construction, control, and safety management. The accident incurred an unexpected cost of £422.7 million, which almost seven times of the contract price to build. The principal contractor paid £1.2 million for negligence. The lessons learned from this accident are the significance of coordination, instrumentation, monitoring, experience, and effective risk assessment. If such accident happen to Preston, the impact would be greater since it is a commercial and highly populated area unlike Heathrow airport. 7. Bibliography Bateman Mike. 2006. Tolley's Practical Risk Assessment Handbook. Butterworth-Heinemann, UK Bell Frederic Gladstone. 2004. Engineering Geology and Construction. Taylor & Francis, UK Blockley D. I. and Godfrey Patrick. 2000. Doing it Differently: Systems for Rethinking Construction. Thomas Telford, UK British Tunnelling Society. 2004. Tunnel Lining Design Guide. Thomas Telford, UK Broome Jon. 2002. Procurement Routes for Partnering: A Practical Guide. Thomas Telford, UK Bunni Nael G. 2003. Risk and Insurance in Construction. Taylor & Francis, UK Carvel, Richard and Beard Alan N. 2005. The Handbook of Tunnel Fire Safety. Thomas Telford, UK Cole Gerald A. 2003. Strategic Management: Theory and Practice. Cengage Learning EMEA, 2003, Singapore Kletz Trevor A. 2001. Learning from Accidents. Gulf Professional Publishing, UK Kaushish S. and Ramamurthy T. 2000. International Conference Tunnelling Asia '2000, 26-29 September, New Delhi, India: Need for Accelerated Underground Construction, Issues and Challenges. Taylor & Francis,, US Lant, Theresa and Shapira. Zur. 2001. Organizational Cognition: Computation and Interpretation. Lawrence Erlbaum Associates, US Raymond Carole. 1999. Safety Across the Curriculum: Key Stages 1 and 2. Routledge, UK Villaescusa Ernesto and Potvin Yves. 2004. Ground Support in Mining and Underground Construction: Proceedings of the Fifth International Symposium on Ground Support, Perth, Australia, 28-30 September 2004. Taylor & Francis, Netherlands Read More