The light at the end of the tunnel: managing challenges at Heathrow Express Project

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Developed by Jose de Jesus Cruz Contreras

Image 1. A view of the site of the collapse at Heathrow Express tunnel in 1994 [1]

The Heathrow Express Tunnel Project was intended as a way to connect Heathrow airport with Paddington station in central London. The project, managed and bided by the British Airport Authority (BAA), was to be constructed by Balfour Beaty (BB), a major and well-known construction firm. As part of the design, BB wanted to introduce the use of a construction technique named New Austrian Tunneling Method (NATM) for the first time in the UK. Consequently, they recruited the services of the technique’s Austrian expert firm Geoconsult. The project was planned to start in 1994.

The project management faced a multitude of difficulties from the start. Among them were a restrictive economic environment, a rigid and complex organization and technical problems with the implementation of a poorly understood technology (NATM). Several decisions taken directly as a result of this scenario jeopardized the entire project and led to the tunnel collapse occurred in the night of October 21st, 1994.

The jointly project management confronted the emergency introducing organizational changes to overcome the disastrous situation[2]; under a new structure, the team gradually repaired the tunnel and finished the project. The namely “Solution team” developed a 12-month plan which included a conservative-approach solution with the construction of a cofferdam (at the time, the greatest ever constructed in Britain). They also recommended continue using NATAM technique for the tunnel construction on the Terminal 4, after an investigation carried out by the Health and Safety Executive (HSE) certified the safety of the method.[3]

Ultimately, the plan succeeded, and the delay was reduced from 12 to only 6 months, and the project-works were concluded in 1998. Subsequently, an HSE investigation on both BB and Geoconsult led to their indictment and prosecution. They were charged with £1,3 million and £600.000 respectively. The case refaced the way to approach construction projects in Britain, including additional requirements and standards for NATM’s tunnel-projects.[4]

This article aims to make an overview of the project, considering its importance over an entire industry that needed to adapt and innovate to stay competitive. The case is a good reference for project practitioners into how a complex and and catastrophic situation can be overturned and learned from.



Figure 1. Heathrow Express System [5]

Project description

The Heathrow Central Terminal Area (CTA) and Terminal 4 stations of Heathrow airport required an efficient way to communicate them to Paddington Station in Central London. The airport’s owner, then a public company named British Airport Authority (BAA), adjudicated the project to the lowest bid (around £60 million) made by Balfour Beaty (BB) under the design proposed by the British building contractor Mott MacDonald. They were required to construct the 8.8 km tunnel and decided to propose the adoption of a technique that had been in use for similar projects, called New Austrian Tunneling Method[4]. The method was seen as a technological solution to cape with the financial restrictions imposed by the budget.

New Austrian Tunneling Method

The New Austrian Tunneling Method (NATM) was developed by L. von Rabcewicz, Leopold Müller and Franz Pacher in a series of articles published in 1964 and 1965. The technique proposed ways to stabilize tunnels under construction using strata and a layer of concrete sprayed. This is why the technique is also named “shotcrete” or “sprayed concrete”. It was first used in the construction of Frankfurt Metro in 1968. The Austrian Society of Engineers and Architects define it as “a method where the surrounding rock or soil formations are integrated into an overall ring-like support structure”[3]. The method was tested for its viability in the clay soil at Heathrow in 1992, confirming the possibility of being used. The method was being also used in several metro lines including the Jubilee Line Extension Project (JLEP) for the construction of tunnels near Waterloo and London Bridge stations, although in not such an extensive manner as in the Heathrow Express project [3].

Contract and Organization

Figure 2. Organizational chart of the project [4]

Balfour Beatty (BB) chose to use the New Engineering Contract (NEC), a new set of contract standards at the time; its first version was released in 1993. The aim of NEC is facilitate the management of the work using plain and simple language to describe the activities that each party must carry out, while enhancing the collaboration across the project stakeholders[6].

BAA set a project management team in line with the NEC requirements: The HEX management team included representatives from BAA, BB, Mott MacDonald and Taylor Woodrow (a British construction company that would function as construction manager). Figure 2 shows the organizational chart of the project, including the role of the Austrian firm Geoconsult, which was not included in the management and was considered a consultant to the engineering division of BB.


As in every project, several challenges raised before and during the project. Some of them would be directly responsible for the collapse at CTA; henceforth are described the ones considered as most relevant.

Project Budget

Arguably, the main driver point of the activities for this project was the budget cost; it is important to contextualize the project on a moment in time when British economy was stagnated and had suffered a recession (1991-1992)[7]. The banks and insurance companies had a risk-averse policy, within a diminishing infrastructure investment environment, which resulted in several postponed or cancelled projects. Although BAA had enough resources to allocate for the financing of Heathrow tunnel, the choosing of the lowest bid meant that the contractor looked for all available options to reduce costs and maintain its adjusted markup.

New Engineering Contract specifications

One of the principle challenges the organization faced was the adoption of NATM technology in the context of British construction industry. This industry was characterized as being highly dependent on standards and codes, "with a high number of disputes being settled through litigation"[2]. Hence, the introduction of the NEC was important to increase the productivity of the sector.

The NEC describes thoroughly the engaged activities to be carried out by each party, and it does using simple wording. One of the central aspects of the NEC was the so-called “self-certification”, which meant that the contractor was in charge of review the quality and advance of their own work. This aspect was considered essential to reduce the bureaucratic charge of the daily management for the HEX team, which in turn would be free to oversee the project itself.

A second and complimentary NEC aspect that represented a major challenge was the “early warning principle”, which stated that the contractor was obliged to inform immediately to the client of any problems presented on the works. In theory this would be done through several middle management reports that would reach the HEX management group, and finally they would evaluate if was needed to inform the client (BAA). However, the reality was that many of the reports which described several problems documented during the CTA tunnel construction were discarded or mismanaged by either the middle managers or the HEX management group.

Technology transfer

As mentioned before, the bidding adjudication called for a tight budget. One way of obtain costs reductions was the introduction of the NATM technology instead of more traditional tunnel construction techniques. Hence, bringing Geoconsult as consultants and supervisors within the construction site was a key move that also impacted on the project finances. However, is worthy to mention that the original offering by Geoconsult to have deployed 3 full-time engineers trained and experienced on NATM construction was reduced to only one. He was charged with the responsibility of “act as site liaison with Geoconsult's design office in Austria, prepare the NATM working sheets as required, interpret monitoring data, and advise Balfour Beatty accordingly”[4]. Three engineers from BB (with scarcely if any training on NATM use) were to function as the missing QA supervisors to assist Geoconsult’s on-site engineer.

Project Organization

Video 1. Geoconsult's history, overview of NATM and the CTA collapse[8]

The project organization, as mentioned before, was complex. The Hex management group had to concentrate mostly on the financial aspects while BB, as main contractor, focused on the project daily scheduled work and the quality assurance. It can be argued that the stream of information was not carried in the most efficient manner. An example of the latter is that although key measures were being recorded and documented, their interpretation and analysis was not always taking into account in the decision process. Furthermore, a lack of communication between the management and the construction department represented a key factor to mismanagement of the data that showed early alarm signs.

Project Quality Review process

An intense and tight schedule called for minor mistakes on the work execution to keep within construction timelines. BB’s construction department assumed the quality assurance responsibility but did not put it as a priority activity nor included it as a major reference on the continuity of the works.

Reworks started to pile up, many being requested by Geoconsult’s field engineer. He had raised several concerns about the quality of the workmanship and asked for additional controls to ensure the tunnel structural integrity. However, his role inside the project structure left him with almost no power to enforce its recommendations; he ultimately depended on Geoconsult to pressure over BB, something that later would be accounted as “poorly done”[4]. During the prosecution trial, one argument held upon the defendants was that BB's managers failed to acknowledge the continuous need of reworks based on the review of its quality [9]. Some signals on the imminent collapse were documented up to 14 days in advance of the event, according to witness expert Sir Alan Muir Wood[4]. The prosecution showed the lack of concern regarding quality inside the project organization using a written communication of BB's director addressed to the Hex Management team, in which he says: “The primary function of the NATM engineers is not quality control. Quality control is the responsibility of the construction teams. This is in accordance with our self-certification scheme, we repeat we have continuous NATM engineering supervision and we do not have project-wide quality problems as you suggest”[4]. Video 1 renders the point of view of Geoconsult regarding the project and the final verdict of the trial.


Figure 3. CTA affected area [5]

The CTA tunnel collapse occurred in the night of October 21st, 1994. Night shift workers that were doing crack repairing around 7 pm noticed the fast enlargement of cracks on the walls, extending to zones where they have already been repaired; from then on, parts of concrete and wire mesh started to fell. The order to evacuate the tunnels came about midnight, and the tunnel collapsed around 1 am of October 22nd. It continued for the next two days, damaging not only the tunnels but also the structures in the surface above them[2][4]. The Figure 3 illustrates the affected zones and mark the sections where surface craters appeared.

Thankfully, there were no fatal causalities nor injured on the event, which occurred on a very busy part of the airport. This was greatly because it happened in the middle of the night. Nonetheless, when the case was presented to the courts by the prosecution, it was treated as a criminal case due its was considered potentially harmful to human lives. In the middle of the media response, the HSE ordered a full investigation and called to stop all other NATM-based constructions until the safety of the technique was properly assessed.

Due the magnitude of the collapse, the insurance company representing the project pressed to settle the responsibilities of each part in court, in the hope to avoid paying large compensations. Henceforth, the requirements of insurance companies for this type of projects would be hardened, demanding the implementation of management mechanisms to ensure project safety[2].

An additional problem was the interruption of transport to and from Heathrow airport by the Picaddilly metro line. This was overcome with the creation of the Heathrow Junction railway station, a temporary station that served until the completion of the project in June 1998 [10].


Video 2. Footage from the CTA collapse, 24Oct1994[11]

The HEX team had to overcome the difficulties of restructuring the information flow inside the project, develop a solution to the crisis and implement a different overview to the quality assurance process. The first was approached by making the HEX team to be in closer contact with daily work advances by having group meetings with the middle management involved in the construction site. The second was the creation of a task force denominated "Solution team". This entity's main purpose was to generate a feasible, efficient and affordable path to reconstruct the tunnel and retake the project.

The latter aspect changed by the incorporation of external overview over the quality. The approach was somewhat mandatory, since the involvement of the HSE increased as part of the investigations on the site.

With the urgent need of additional resources came the budget and contract restructure negotiation. The controversies around the use of NEC were postponed, while the contract was adjusted to a more traditional version, with a higher involvement of BAA. From the technological point of view, the "solution" team proposed a conservative plan, based primarily on a cofferdam. This approach came as no surprise, since the most important objective was to remediate the problem as fast and save as possible while incurring in the lowest possible cost. The “solution” team offered a 12-month integral plan that addressed not only the construction issues, but reshaped the organization structure, with special stress in the internal communication.

Technological solution

As mentioned before, the "solution" team came with the idea of a cofferdam to free the collapsed area in the tunnel; the size of the operation made the cofferdam the largest ever constructed in the U.K. up to that moment[12].

Despite the previous problems, and in line with the report of the HSE which considered that “[p]rovided careful account is taken of all the issues in …[the HSE report]… review, it has proved possible for NATM work to proceed in safety..."[3], the "solution" team supported the decision to continue with the use of the same technology for the construction of the tunnels at Terminal 4.

Organizational solution

As for the organization, the “solution” team brought a new mentality to the project. The narrative changed to be one focused on cost-reduction, and was redirected towards one of motivation to finish the project on quality and safety as key drivers. Since any collapse responsibility would be acknowledged by the competent judiciary authority, there was no point in doing a witch hunt. Therefore, the Hex management group promoted a culture of no-blame, which did not mean to overlook responsibilities but rather prevent a division within the project structure. This helped to align all parties into a single goal.

Information flow

The communication strategy was modified too. All decisions were transmitted through formal notifications and the receivers had to confirm that they have been informed. This process could take more time but in turn helped to increase the workers’ involvement on the project, since they could know exactly what was expected from them. Another initiative was to held weekly project advance meetings to review the status with all involved parties.

Decision making process

The decision process was opened to allow the participation of the operation and construction departments, and ensure the acknowledgement of their feedback. The approach had two clear intentions: a) to empower workers and deepen their involvement on the project development, and b) to increase the early notification of potential issues, so they could be adequately addressed. Altogether combined with a culture of documentation, where all parties became accountable of the inputs and decisions took, documented on a signed minute of their weekly project meetings.

Under these management changes, the project advanced at good pace. The conservative solution worked: the cofferdam allowed the cleaning and repairing of the collapsed sections of the tunnel. Meanwhile, the HSE had concluded the assessment of the NATM technique safety and issued a series of recommendations for its use; they also concluded that “…[t]he existing statutory provisions, and in particular CDM, provide a comprehensive system for the regulatory control of risk including the assessment of competencies. HSE concludes there is no need for further legislation specifically to address the risks arising from NATM”[3]. The other projects that used the technique restarted in the U.K.. By mid 1996 the works of tunnel refurbishment continued according to the original plan, and the gap started to reduce from the initial 12-month towards only a 6-month delay from the originally projected deadline. Finally, the trains started to operate on June 23rd, 1998.


In the words of Justice Peter Cresswell during the trial: "This was one of the worst civil engineering disasters in the United Kingdom in the last quarter of a century”[13]. And it was so not only by the magnitude of the collapse and the construction importance, but also in the way the project was handled. For a sector of the size and history like the British construction industry, the failure represented an inflection point in several senses. Some are mentioned in the lessons learned.

Lessons learned

  • The professionalism of the industry was challenged, and key actors of the industry like BB and Mott-MacDonald had to face their reputation damaged for allegations of lack of supervision and poor project management. The adjustment of revised Management practices[14] and the different use of construction contracts [15] would help to overturn such image.
  • An overconfidence and difficulty to adapt to business challenges was revealed, including disregard in the understanding and adaptation of technologies. In that sense, is important to review how professional associations such as the Institution of Civil Engineers (ICE) responded to the event. In the case of ICE, they issued the guideline “Sprayed Concrete Linings (NATM) for tunnels in soft ground” (1996)[16], which helped to standardize somewhat the use of NATM technology in the U.K..
  • The cost-reduction orientation of the management at the beginning of the project impacted on the necessary quality assurance and risk assessment that is required in construction works. After the collapse, there was a hardening on the risk management regulation on the construction industry. An example of this change can be seen in the project for the construction of Terminal 5[14].
  • It showed that the HSE supervision was far from the expected. No warnings were issued by inspections carried out at the construction site. During the trial against BB and Geoconsult, the entity also was called of being partial and biased on their account of facts, and received only a small compensation from the total amount of the imposed fines[4].
  • The industry as a whole and the government recognized the need to implement new working standards to maintain Britain as a leader within the construction sector. One of such initiatives was the document “Rethinking Construction: The Report of the Construction Task Force” (1998)[17], that provided the outlines for the industry reconfiguration during the early 2000-decade.


In the end, is interesting the ability of the project management to reconvene the work and correct most of the issues that led to the collapse. The main differentiator in this project was not the introduction of a new technology (although is an important aspect of it), but the intensive process of management adaptation to a new business and industry reality, and the capability of identify the key aspects to be corrected within a large and complex organization.

If anything, the project also represents a great example of how to convert a tremendous disaster into an industry revolution.

Annotated Bibliography

From the list of reviewed material to document this article, in the author's opinion, the following 3 are the best sources to get an initial understanding of the case and its implications from different perspectives. Two of them can be easily accessed through their online versions:

This assessment contains generalities about Sprayed Concrete Lining (SCL)-NATM method from a technical point of view. It was prepared by the HSE in response to the CTA collapse. It also contains a review of the state of the art of the technique, and provides a history of the evolution and use of method in projects around the world (including a list of similar incidents). Finally, it offers HSE recommendations on the use of the technique. Is a good initial point to understand the technology.
This online divulgation article offers the journalistic approach to the review of the case. It offers a general overview of the case, based from the chronicle of the prosecution trial against BB and Geoconsult, taking quotes and facts from the people involved in them. The article also offers a contextualization of the case and some of their repercussions. The author considers this the best initial approach to understand the key steps leading to the collapse coming from a specialized but not technical source.

As for the third, this is a confidential article accessible only for academic purposes:

  • Aalvik, M., Cruz Contreras, J. J., Guerra, P., Jónsdóttir, S. L., van der Mieden, J., Tange I. & Vinggaard Kjeldsen, C. (2016). Influence of the Heathrow Express tunnel collapse on the British tunneling industry. Article prepared as part of the “Management of Change In Engineering Systems” Course spring 2016, Danmarks Tekniske Universitet (DTU)
This academic article was prepared as part of the course Management of Change In Engineering Systems from Denmark's Tekniske Universitet (DTU). The article takes on the case from the perspective of the management of change and analyzes the decisions taken by the management before, during and after the collapse using two models: Kotter’s integrative model of organizational dynamics; and Cummings & Worley's typology of interventions. The article makes a review of the documents mentioned in this wiki article, and it also report on the interviews held with two members of the project (both started at the project after the collapse). Due the confidential character of the opinions expressed by the interviewees and according to their desires, the article cannot be distributed for publication.

For additional and more technical references, the interested reader may like to review:

  • Health and Safety Executive (2000). Collapse of NATM tunnels at Heathrow Airport. A report on the investigation by the Health and Safety Executive into the collapse of New Austrian Tunnelling Method (NATM) tunnels at the Central Terminal Area of Heathrow Airport on 20/21 October 1994, London, U.K.: HSE Books Available for purchase
The technical official response of the HSE that goes further into the full details of the event. This document is not free for access and was not available for review during the elaboration of this article.
  • Major Projects Association (2007). T5 Case Study, Seminar 136 held at the Cavendish Conference Centre, London. 23rd October 2007. retrieved 16Sep2016 Available online version,
An account of the project, with a technical review from an expert of the project construction field.
  • ICE (1996). Sprayed Concrete Linings (NATM) for tunnels in soft ground, Institution of Civil Engineers design and practice guides. London: Thomas Telford Publishing. consulted on 16Sep2016 Available online version
The Industry standard on the technique, still valid until this date.


  1. Institution of Civil Engineers Website consulted 13Sep2016
  2. 2.0 2.1 2.2 2.3 2.4 Aalvik, M., Cruz Contreras, J. J., Guerra, P., Jónsdóttir, S. L., van der Mieden, J., Tange I. & Vinggaard Kjeldsen, C. (2016). Influence of the Heathrow Express tunnel collapse on the British tunneling industry. Article prepared as part of the “Management of Change In Engineering Systems” Course spring 2016, Danmarks Tekniske Universitet (DTU).
  3. 3.0 3.1 3.2 3.3 3.4 Health and Safety Executive (1996). Safety of the New Austrian Tunneling Method (NATM) Tunnels. London, U.K. Available online version, retrieved 14Sep2016
  4. 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 Wallis, S. (1999). Heathrow failures highlight NATM (abuse?) misunderstandings. Tunnel, 3/99, 66–72. Available online version, retrieved on 09Sep2016
  5. 5.0 5.1 Clayton, C. (2008). The Heathrow Express Tunnel Collapse, slideshow from the Advanced Course on Risk Management in Civil Engineering, LNEC, Lisbon, Nov 17-22, 2008 Available online version, retrieved 13Sep2016
  6. NEC history, consulted on 13Sep2016
  7. UK Recession of 1991-92 consulted on 14Sep2016
  8. TunnelTalk (2013, 09 Oct). Geoconsult settles the Heathrow case TunnelTalk youtube video
  9. Harper, K. (2000, 6 July). Managers 'overlooked risk' in airport tunnel collapse, The Guardian, online version consulted on 12Sep2016
  10. Heathrow Junction railway station (n.d.). Retrieved 14Sep2016 from the Wiki: Wikipedia online article
  11. Associate Press (1994, Oct 24). UK: Office Block Collapse at London Airport, Video available at AP Archive
  12. Findlay, J.D., (2000). Construction of the CTA cofferdam at Heathrow Airport, London. Geotechnical Aspects of Underground Construction in Soft Ground, Kusakabe, Fujita & Miyazaki (eds). Rotterdam. Available online version, retrieved 16Sep2016
  13. N.A. (1999, 15 Feb). Business: The Company File Record fine after tunnel collapse, BBC News, online version consulted on 12Sep2016
  14. 14.0 14.1 Major Projects Association (2007). T5 Case Study, Seminar 136 held at the Cavendish Conference Centre, London. 23rd October 2007. Available online version, retrieved 16Sep2016
  15. Loots, P., & Charrett, D. (2009). Practical Guide to Engineering and Construction Contracts. Sydney, AU: CCH Australia Limited. Available online version, consulted on 16Sep2016
  16. ICE (1996). Sprayed Concrete Linings (NATM) for tunnels in soft ground, Institution of Civil Engineers design and practice guides. London: Thomas Telford Publishing. Available online version, consulted on 16Sep2016
  17. Egan, J. (1998). Rethinking Construction: The Report of the Construction Task Force, U.K. Available online version, retrieved 16Sep2016
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