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GroBbritannien Heathrow failures highlight NATM (abuse?) misunderstandings

Shani Wallis

In February 1999 the heaviest Following a quite extraordinary four Beatty is set against an original cution's main expert witness fines ever imposed following trial - which has actually left no party contract value of £ 60 million and report had been directed and prosecution by the British Health & to the proceedings unscathed - against a company within a large in some cases written by the Safety Executive were levied against Geoconsult has lodged an appeal corporation that accounts for about leading HSE inspector. The re- and Geoconsult against both the conviction and the 10% to 15% ofthe group's £2 billion port could not be relied upon following collapse of NATM station sentence. It claims that HSE annual turnover. The fact that Bal- as being independent and un- tunnels on the Heathrow Express Rail "breached its paramount legal four Beatty admitted guilt, the biased. As a result prosecu- Link Project at Heathrow Airport in obligation to prosecute fairly" and judge said, mitigated in its favour tion withdrew the report in its in October 1994. Balfour that rulings on procedural orders although it was made evident entirety and the court Beatty, tunnelling contractor on the "resulted in prejudice" against the during the trial that Balfour Beatty allowed prosecution to £440 million project, pleaded guilty company. Against the sentence it "must bear greater responsibility depend on the alternative to violating two counts ofthe claims that the fine is excessive and for the collapse". expert witness of Sir Alan country's Safety at Work Act 1974 overlooks guidelines that fines should Muir Wood and of Prof John and was fined £1.2 million plus reflect the gravity of the offence but One of the major losers in this Hutchinson. These reports £100,000 toward prosecution costs should not imperil the existence case is the prosecuting agency were introduced by and were given 14 days to pay. ofthe company. The total £600,000 itself. The HSE was severely prosecution at a preliminary fine for Geoconsult is levied against criticised by the trial judge for its hearing in November 1998, it Geoconsult, as specialist designer an original contract value of £1 conduct of the case and was was said, to support the origi- to Balfour Beatty for the NATM million and against a medium sized awarded only £200,000 of the nal and subsequently with- works on the project, denied the consulting company. The £880,000 claim for costs. In the drawn expert witness report charges but was found guilty by a $1.3 million total fine for Bal- opening days of the trial and by submitted by Mr Guy Lance jury of 12 after a 26-day criminal trial chance, the defence team found of WS Atkins. In response, de- at the Old Bailey Criminal Crown that much of the prose- fence made application for Court and was fined £500,000 with the case to be dismissed on £100,000 towards costs and was the grounds of "abuse" and given two-and-a-half years to pay. Balfour Beatty's lowest bid £60 million contract was to build 8.8km applied also for the expert of shield-driven running tunnel and various NATM caverns including witness of Muir Wood and The two charges laid against each the underground station complexes at CTA and Terminal 4 on the Hutchinson to be disallowed company were for failing in their estimated £440 million Heathrow Express Rail Link Project. as substitute. Both applica- duty to ensure the safety of their Geoconsult was specialist NATM design engineer to Balfour Beatty. tions were denied and the employees during of NATM was specified for design of the stations following a successful trial proceeded. This matter is the NATM station tunnels at the CTA trial of the method in London Clay at Heathrow in 1992. The trial was to be re-examined in Geocon- (Central Terminal Area), and failing designed and supervised by the UK office of Austria's Dr Sauer sult's appeal. So although HSE to ensure the safety of those not in company and was built by the Kier/Lilley/Kunz UK/German joint obtained a conviction, it was effectively fined £680,000 - their employ (the general public), by venture. This was the first use of NATM in London Clay and the not including the cost of the exposing them to danger. For method was subsequently adopted for the Waterloo and London Lance report. Geoconsult the charge included Bridge stations on the Jubilee Line Extension of London's technical supervision of the works. Underground. At no time in the trial did HSE or prosecution suggest The trial . that NATM as verified by the trial tunnel or designed by Geoconsult During the trial, evidence Shani Wallis, Laser Line, for the Heathrow Express was defective in any way. Prosecution and revealed extremely poor Surbiton/UK the HSE in its report "Safety of NATM with particular reference to workmanship; major flaws in London Clay" stated that NATM is a safe and appropriate tunnelling construction management; method in London Clay "providing enough care is taken" and that the and questionable Heathrow NATM structures now open to the public since mid 1998, contractual arrangements. are safe. Miners in the tunnelling gangs told of difficulty in 66 Tunnel 3/99 constructing the invert joint of the NATM side-wall drift London Heathrow Express Link

excavation sequence; of problems with blockages and delayed delivery of shotcrete; of regular changes in the personnel in the gangs and of little continuity of routine. Con- struction foremen and shift engineers told of pressures from management to improve productivity and make up for delays Site and supervising en- gineers raised concerns about over-excavation of rounds by the miners; inexperience and lack of skill in the crews; and higher than expected surface settlement leading to inspection and repair of inverts where shotcrete was 50mm instead of 250 to 300mm 3 Plan of the excavation works completed at the time of the collapse of the Central Terminal Area thick; where there was insufficient overlap or no starter bars at all in construction joints; and where shotcrete was sprayed over rebound. Senior engineers 1 It was on the night of 21 Nov. 1994 that the Central Terminal Area station tunnels collapsed causing questioned the apparent lack of extensive damage to the surface an experienced supervision team; the apparent disregard of All of these flaws culminated Eventually the teams were or- the many CARS (corrective action in October 1994 with the ul- dered to vacate the tunnels at The prosecution requests) raised by any engineer timate collapse of the CTA NATM about 12am amid the sound of case noticing poor workmanship; tunnels. Cracks in the shotcrete cracking and the sight of shotcrete apparent disregard of SDNs started to propagate farther, particles raining down. At about HSE as the prosecuting (system defect notices) raised by faster and grew wider during the 1am the abandoned tunnels agency claimed that the col- the project management team early hours of the night shift started to collapse and continued lapse "was the worst civil en- for the attention of senior (started at 7pm) and teams were over the two following days gineering disaster in the united contract managers; the being moved from one area to creating a hole on the surface and Kingdom in the last quarter of application of "self certification" another to try and repair cracks causing extensive damage to a century" and that it was only as part of the construction and replace lumps of shotcrete surface structures. All stabilised on by chance that no-one was contract; and early relaxation of as they fell and wire mesh burst the third day and with much of the seriously injured or killed. As the already disfunctioning through the green shotcrete of underground cavity infilled with well as endangering the lives auditing role by HEX of the earlier repairs. concrete. of the workers, prosecution contractor's self-certification suggested that the conse- system. quences for the public could

Tunnel 3/99 67

GroBbritannien United Kingdom have been disastrous, if the collapse at one of the world's busiest airports had occurred during the day, and if the con- course tunnel had "unzipped" to beyond the Piccadilly Line tunnels of the London under- ground system which lie above the Express Rail Link tunnels and some 70m out in front of the collapsed zone (Figs 2 and 3). Prosecution claimed on the basis of expert witness that monitoring data indicated that the collapse was evident up to seven days before the event, that Geoconsult was "the 3 Plan of the excavation works completed at the time of the collapse of the Central Terminal Area watchdog that did not bark". certification in that Balfour on-going repairs in the invert of double production by the end Sir Alan Muir Wood for Beatty felt HEX should not be the CTA concourse had been of the week. He demands that prosecution stated that in his involved". He felt, he said, that raised", (in evidence Sir Alan we open all six faces. Panic all opinion, the collapse was caused Balfour Beatty were paying "lip Muir wood retorted that "Nero round". "Cracks in the tempo- by the defective invert. He service" to self certification. in was fiddling while Rome was rary wall - expert foreign claimed that recorded his read statement Bob Gee, burning".) in defence, it was sounding gentleman to inspect monitoring data and other engineering design manager in made clear that Geoconsult was and instruct." "Oh dear, oh contemporaneous evidence HEX, said other than increasing acting as part of Balfour dear, oh dear. Horizontal cracks indicated that collapse was the initial prediction of 9.34mm Beatty's own engineering in concourse tunnel. The witch imminent up to 14 days before. of settlement over the department under manager Ian hunt starts now." "Big He criticised the NEC form of concourse tunnel at CTA, the Massey; and that Geoconsult movement in the concourse contract as inappropriate for HEX team were satisfied with personnel were not invited to crown at chainage 31 to 40m. tunnelling contracts; that self- Geoconsult's NATM design and project meetings; were not on Time to open up the invert for certification as a method of the baseline criteria and the distribution list of letters or a look see.” "Work on inverts quality control had failed; and assumptions used. There was meeting records; and were not [in section back to the shaft] that (under cross examination) concern however of apparent party to various decisions still on-going. You might as well "it is very unfortunate for lack of supervision and lack of including it was claimed the take the whole section out." in Geoconsult to find itself where it experience in the construction programme of compensation his evidence Muir Wood is" and that "morally it is very teams as work started and a "jacking" under Camborne suggested that removal of a hard luck for them." He said that major concern that the process House in August 1994, nor the large section of the tunnel's "the way in which the whole of self-certification and its audit decision to stop concourse infill clay over the defective management of this contract by the HEX team was not tunnel invert repairs in August invert (rather than in 2m was proceeding meant there working. He said that while rather than continuing back to sections as instructed and was a great break between engi- compensation grouting had the access shaft; nor the carried out for the earlier re- neering and construction which, been used in August 1994 to instruction to open the two pairs), together with starting to my mind, is the fundamental counteract higher than parallel upline and downline the parallel platform tunnels, ill effect which led to all these expected (18mm) settlement station platform tunnels in late initiated the collapse. things happening". He said that under Camborne House above September to make up for liability for the collapse "should the CTA concourse tunnel as it delays of 28 days and 80 days The case for the extend to those who were passed underneath, the HEX on these headings. Further defence putting these sorts of contracts team was not alarmed by evidence read by prosecution Of all the collapse reports together". monitoring data they had seen from the Balfour Beatty section produced so far, perhaps the to date. "We did not spot the engineers log book prior to the most thorough is that produced Jonathan Allen, CTA area lead up to the collapse," he collapse gives an indication of by defence expert witness Prof. manager in BAA's (the private said, and that at the last the climate on the site. Entries Reinhard Rokahr of Hanover owners of Heathrow Airport) progress meeting between HEX read: "Alan (more muck) Myers university. Sir Alan Muir Wood HEX (Heathrow Express) man- and Balfour Beatty on the day [Balfour Beatty's construction admitted that his report was agement team said that he was of the collapse, "neither project director] demands we prepared in a week "concerned with the lack of settlement nor understanding about self 68 Tunnel 3/99 GroBbritannien United Kingdom and used "rough back of an envelop” calculations; the Guy Lance expert witness report was withdrawn; an expert witness report produced by Profs. Mair and Potts of Cambridge University for Balfour Beatty was not made available, given Balfour Beatty's guilty plea; and the incident Report, called for by the UK government and being prepared as a statutory duty by HSE with input from Guy Lance of WS Atkins, Martin Thurgood of HSE, and Sir Alan Muir Wood among many others, is yet to be 4 BAA, known in the UK as a progressive client, chose the New Engineering Contract (NEC) for the project and published. to adopt a system of "self certification" whereby contractors certify their own work and keep their own quality assurance records. To manage the project, BAA established the HEX team comprising engineers from Although Prof Rokahr criti- Mott MacDonald, BAA'S project engineer and designer of all the permanent works; , cised the lack of on-site NATM appointed before contracts award as construction manager; and members of its own engineering and authority at Heathrow; lack of management staff, in addition, Mott MacDonald was appointed by BAA and under separate contract to experience among the field monitor and control all surface settlement issues during construction of tunnels under the airport facilities. It engineers, the tunnelling fore- undertook the same responsibilities for Balfour Beatty under a different contract and Keller was engaged as the specialist contractor to undertake compensation grouting to control surface settlement under sensitive men and the crews; poor quality structures. Following the collapse, all parties to the project remained engaged and in a truly single minded of the monitoring instru- project oriented approach, some quite remarkable engineering and construction work, including NATM work mentation data; lack of full time in the stations, was undertaken to restore the situation and complete the project just 6 months later than geotechnical geologists within schedule - but at what cost depends where you start counting an NATM supervision team that already number too few; limited bore down on the concourse ening of the clay body caused by for the collapse given the instrumentation data available; tunnel which, with its defective starting the two parallel platform circumstances of the work, the serious omissions in the invert, could not act as a closed tunnel headings, and a soaking of evidence, and the geotechnical installed instrumentation ring. This imparted heavy loads the clay through the collapsed eye data available. He said that the regime; and of the "inadequate" onto the upline platform tunnel of an escalator box (excavated speed of collapse could not be computer software system where the new shotcrete could overhead and under a earlier predicted and that workers provided by Balfour Beatty for not carry the exceptionally high contract) could have initiated the were not exposed to risk until processing the instrumentation loads and failed. Thereafter the landslide. He claims that deforma- immediately before the collapse. data; he did state that there was block subsided further and tion and settlement readings taken sufficient recorded data to caused the defective invert of the under Camborne House in August Hutchinson, professor of indicate that: "In my view, the concourse tunnel to fold in on 1994, with an equally defective geology at imperial College as an causation of the collapse, in all itself and the upper part of the invert, were higher and did not expert witness for prosecution, probability and I think bordering concourse to settle by ap- cause collapse than those stated that London Clay is a well on certainty, is a large scale slide proximately 2m but without recorded, in the area that did documented, largely of the clay mass in the zone be- leading to a complete collapse of collapse in October. All readings, homogeneous, uniform and tween the downline platform the crown. The defective invert, including the last taken before the extensive body of over tunnel north heading and said Rokahr, and its ongoing collapse, he stated, were well consolidated sedimentary clay Camborne House (Figs 2 and repair could not on their own within the design's critical level with very few discontinuities and 3)." The collapse, he claims, have triggered the collapse. The criteria. Rokahr's expert evidence none identified in the area of the started as horizontal shear report by Mair and Potts he said, is based on the theory that some CTA that could have caused a cracks in the walls of the ad- declared that even with part of unforeseeable and completely landslip such as the one vancing side wall drift of the the invert completely removed, unpredictable behaviour or described by Prof Rokahr. He did downline platform tunnel. After the tunnel, as designed, should geotechnical mechanism in the however criticise the site losing support in the area of the still have stood up for up to 80 clay body is the only explanation investigation carried out by Mott downline platform tunnel, a days. He suggested that a soft- MacDonald as being monolithic block of clay created "preliminary" and "surprising if a by a number of bored piles near tunnelling expert the working shaft and acting like stiff dowels,

70 Tunnel 3/99 GroBbritannien United Kingdom did not carry out a further sumed the role of construction The verdict was stopped near the end of the investigation". quality control supervision. This After closing statements the Heathrow trial by the judge on. was confirmed in a letter from jury was dismissed to consider the grounds that even though the In a reverse of usual criminal Alan Myers, project director for its verdict. In his instructions, four accused were not on the site prosecution proceedings, the Balfour Beatty, to the HEX the judge asked the jurors to when they clearly should have burden of proof is on the defence management team a month consider: Did Geoconsult been, the event and its to prove that all reasonably before the collapse that: "The endanger the lives of its workers consequences could not have practicable was done by their staff primary function of the NATM and those of the general public been avoided. Equally, is to avoid the collapse and avoid engineers is not quality control. and did they do every thing judgement by a lay jury of such endangering the lives of workers Quality control is the "reasonably practicable" to complex technical matters and the public. To this end responsibility of the construction avoid such risks? If yes to the appropriate? The industry itself Geoconsult argued that its teams. This is in accordance with first part and yes to the second knows how difficult it can be to responsibility on-site was greatly our self-certification scheme, we part - not guilty. If yes to the discuss technical engineering reduced by Balfour Beatty in that repeat we have continuous NATM first and no to the second - principals even among skilled its original proposal for three full engineering supervision and we guilty, it took the jury 10h - and professional engineers. time employees (an experienced do not have project-wide quality a return to the court room to site engineer and two full time problems as you suggest." Three hear further evidence about the So, Although the trial is over, the NATM construction foremen) had engineers were provided by collapsed escalator box and the debate continues. First the result been reduced to one site engineer Balfour Beatty to assist 13m3 of concrete pumped in to of Geoconsult's appeal is awaited whose responsibility was to act as Geoconsult's engineer in the field fill the void created - before it and at some stage, the site liaison with Geoconsult's de- but these had little or no on-site returned a unanimous verdict of international tunnelling industry sign office in Austria, prepare the or NATM design experience and guilty against Geoconsult. will finally, after more than four NATM working sheets as required, had to cover all NATM areas of years, have sight of the official HSE work on the full project. interpret monitoring data, and in the aftermath of the trial, the report into the incident itself. advise Balfour Beatty accordingly. UK technical trade press has They further argued that the one In his efforts Adrian Kattinger Wallis, S.: Heathrow rises from the carried numerous letters and mire and shines. Tunnel 6/1996, p. 6 on-site Geoconsult engineer, warned of poor workmanship and articles on various aspects of Adrian Kattinger, tried to exert the the possible consequences to the case including criticism or type of authority usually invested Balfour Beatty's engineering and support of the New Engineering Tunnel in the NATM site Engineer on the management staff and to his Contract and of self-certification Sonderdruck- Continent and through a full team colleagues in head office in while in the meantime the of equally skilled and experienced Austria. He raised several CARs, actual cause of the collapse service field engineers, but against all the and had his instructions overruled remains a point of professional Sonderdrucke unserer - a point clearly illustrated in the odds. dispute. Fachartikel sind jeder- zeit trial evidence when the NATM möglich-zu einem Kurt Laubichler, Geoconsult's head field engineer on night shift asks On addition other serious issues erschwinglichen Preis: für of NATM work at HEX, said in an of his fellow engineer "Was it are being discussed. For Ihre Werbung, für interview with HSE that Geoconsult agreed on the day shift that there example is a criminal court was "requested in writing by is no need to progress invert re- really the most appropriate Schulen, Weiterbildung Balfour Beatty, after award of pairs in the concourse any further venue for investigating such und andere Veranstal- contract I think, that we should back toward the shaft?" A "NO!" events? In an open letter to a tungen. propose one man to work within in Kattinger's hand writing UK technical trade magazine the framework of the services indicates the answer but Geoconsult stated that had the Wenn Sie interessiert sind description". He said Geoconsult regardless, repairs of the con- collapse occurred in Austria, an und Einzelheiten wissen course tunnel invert (following had no choice other than to agree. official investigation would have möchten - bitte rufen Sie Balfour Beatty claimed that it had excessive settlement and been conducted but "it is die Redaktion an: sufficient NATM experience from compensation grouting under improbable that criminal +49 (0) 52 41 / 80-19 43. the and other pro- Camborne House during August proceedings would have jects and that it could provide all 1994) was stopped at chainage resulted in a case where nobody the necessary site foremen, shift 54m. it was during subsequent was injured or killed". The engineers and field engineers. With repair of the invert from chainage criminal case against the four only one Geoconsult engineer on- 54m back to the working shaft in construction site managers site, defence claimed it was implicit October that the tunnels col- following the NATM tunnel that Balfour Beatty had as- lapsed. collapse in Munich just weeks before the Heathrow collapse, and which killed four people,

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