Industrial Relations Commission of New South Wales in Court Session CITATION : WorkCover Authority of New South Wales (Inspector Peter Hannan) v Bitupave Limited, trading as Boral Asphalt [2000] NSWIRComm 50 PROSECUTOR WorkCover Authority of New South Wales (Inspector Peter Hannan) PARTIES : DEFENDANT Bitupave Limited, trading as Boral Asphalt FILE NUMBER: IRC 5867 and IRC 5868 of 1996 CORAM: Hungerford J Evidence - Circumstantial evidence - Expert evidence - Whether each fact to be satisfied beyond reasonable doubt to enable inference of guilt - necessary intermediate facts - Rule relating to circumstantial evidence - Ultimate inference of guilt CATCHWORDS : Occupational Health and Safety - Alleged failure to ensure the health and safety of employees operating a bitumen spray tanker - Unsafe system of work - Failure to instruct and train - Ignition of a flammable cloud of vapour - Explosion - Fireball - Whether one or two offences - Whether separate and distinct charges - Causal connection of defendant employer with the detriments to safety - Whether reasonably practicable for defendant to comply with statutory obligation - Whether caused in circumstances over which the defendant had no control and where impracticable to make provision - Defences not made out - Offences proven LEGISLATION CITED : Occupational Health and Safety Act 1983 s 15(1) s 15(2) s 16(1) s 17 s 53 Boral Gas (NSW) Pty Ltd v Magill (1995) 37 NSWLR 150, (1995) 58 IR 363 State Rail Authority of New South Wales v Dawson [1990] 37 IR 110 McMartin v The Broken Hill Proprietary Company Limited (unreported, Supreme Court, Grove J, 86/20002, 05/02/88) Haynes v C I & D Manufacturing Pty Ltd (1994) 60 IR 149 Rech v F M Hire Pty Ltd (1998) 83 IR 293 Drake Personnel Ltd, t/as Drake Industrial v WorkCover Authority of New South Wales (Inspector Ch'Ng) (1999) 90 IR 432 WorkCover Authority of New South Wales (Inspector Ankucic) v McDonald's Australia Ltd (unreported, Walton J, Vice-President, IRC98/1104-1106, 04/02/00) Kirkby v A & M I Hanson Pty Ltd (1994) 55 IR 40 Hannah v Ricegrowers Co-operative Ltd (unreported, Fisher P, 90/88, 20/11/90) Independent Cargo & Wool Services Pty Ltd v Mingare (unreported, Fisher P, Glynn and Peterson JJ, CT92/1041, 10/03/94) CASES CITED : Tyler v Sydney Electricity [1993] 47 IR 1 Warman International Ltd v WorkCover Authority of New South Wales (1998) 80 IR 326 Watson v Southern Asphalters Pty Ltd (1996) 83 IR 446 WorkCover Authority of New South Wales (Inspector Viesis) v Thiess Contractors Pty Ltd (1996) 85 IR 12 WorkCover Authority of New South Wales (Inspector Dowling) v Overtop Pty Ltd (1998) 86 IR 319 McVernon v Royce Roofing Industries Pty Ltd [1988] 25 IR 383 Cullen v State Rail Authority (NSW) [1989] 31 IR 207 R v Cable [1947] 47 SR (NSW) 183 R v Rothery [1925] 25 SR (NSW) 451 Shepherd v The Queen (1990) 170 CLR 573 Chamberlain v The Queen [No 2] (1984) 153 CLR 521 HEARING DATES: 10/22/1997; 10/23/1997; 10/24/1997; 03/02/1998; 03/03/1998; 08/12/1998; 08/13/1998; 03/22/1999; 03/23/1999; 08/23/1999; 08/24/1999; 08/25/1999; 09/23/1999 DATE OF JUDGMENT: 04/06/2000 PROSECUTOR Mr D J Brezniak, of counsel SOLICITOR Mr B Whitehead WorkCover Authority of New South Wales LEGAL REPRESENTATIVES: DEFENDANT Mr J B Simpkins, of counsel SOLICITOR Mr A Morrissey Murphy & Moloney with Pryor Tzannes & Wallis JUDGMENT: - 94 - INDUSTRIAL RELATIONS COMMISSION OF NEW SOUTH WALES IN COURT SESSION CORAM: HUNGERFORD J Thursday, 6 April 2000 MATTER No IRC 5867 of 1996 WORKCOVER AUTHORITY OF NEW SOUTH WALES (INSPECTOR PETER HANNAN) v BITUPAVE LIMITED, TRADING AS BORAL ASPHALT Prosecution pursuant to s 15(1) of the Occupational Health and Safety Act 1983. MATTER No IRC 5868 of 1996 WORKCOVER AUTHORITY OF NEW SOUTH WALES (INSPECTOR PETER HANNAN) v BITUPAVE LIMITED, TRADING AS BORAL ASPHALT Prosecution pursuant to s 15(1) of the Occupational Health and Safety Act 1983. JUDGMENT 1 The Court has before it two matters being prosecutions by Peter Hannan, as an inspector of the WorkCover Authority of New South Wales, of Bitupave Limited, t/as Boral Asphalt for breaches of s 15(1) of the Occupational Health and Safety Act 1983. Section 15(1) imposes the obligation on an employer to "ensure the health, safety and welfare at work of all the employer's employees". The charges 2 The first charge (Matter No IRC5867 of 1996) as contained in the initiating summons was in the following terms: On 17 November 1994 at Blackneys Road, Stokers Siding, the defendant, being an employer DID FAIL to ensure the health safety and welfare at work of all its employees contrary to section 15(1) of the Occupational Health and Safety Act, 1983, in such case made and provided. The particulars of the charge are : a. Failed to provide a system of work that was safe and without risks to health in respect of measuring the contents of the bitumen tank on a bitumen spray tanker. 3 The second charge (Matter No. IRC5868 of 1996) was stated in the initiating summons in the following terms: On 17 November 1994 at Blackneys Road, Stokers Siding, the defendant, being an employer, DID FAIL to ensure the health safety and welfare at work of all its employees contrary to section 15(1) of the Occupational Health and Safety Act, 1983, in such made and provided. The particulars of the charge are: a. Failed to provide such information, instruction, training and supervision of its employees as may have been necessary to ensure their health and safety at work in respect of measuring the contents of the bitumen tank on the bitumen spray tanker. 4 The defendant pleaded not guilty to each charge. The occurrence 5 The prosecutions arose out of an incident occurring at about 5.00 pm on 17 November 1994 at Blackneys Road, Stokers Siding near Murwillumbah in the State during the use by the defendant of a tanker truck to spray bitumen onto road surfaces in the course of road sealing operations. Two of the defendant's employees, Kevin James Newton and Henry Wayne Anolek, were working on the tanker and had sprayed bitumen onto parts of Blackneys Road and to an adjacent cul-de-sac; the tanker was parked at the end of the cul-de-sac opposite a private residence when Mr Newton, who was assisting Mr Anolek as the driver in the operation, proceeded to measure the quantity of bitumen remaining in the tanker and for that purpose he mounted the top of the vehicle. What then occurred, as the prosecutor's counsel (Mr Brezniak ) described in his opening submissions, was that "the dipstick was under the hatch in a container and he had to lift the hatch, push in the dipstick and measure the amount of bitumen in the tank. He closed the lid and apparently moved to leave the top of the tanker to go to the rear when he was enveloped in a very large explosion which apparently involved the ignition of an inflammable gas which had come out of the tank". Circumstances and particulars of the offences 6 Details of the allegations against the defendant were contained in an affidavit of Mr Hannan, annexed to each of the initiating summonses, in the following terms : 5. On 17 November 1994 ("the date of accident") in the course of their employment, Newton and another worker employed by the defendant as a driver, carried out bitumen sealing operations at Blackneys Road, Stokers Siding, via Murwillumbah, New South Wales. Bitumen was sprayed to the road surface from a bitumen spray tanker owned and operated by the defendant. Two coats of bitumen had been applied to Blackneys Road and one coat to a private driveway connected to Blackneys Road. At intervals during the bitumen spraying operation the practice of "purging the lines" to remove bitumen residue from the spray lines is carried out by forcing a cutter solution through the spray lines with the bitumen pump at a pressure of approximately 50 psi. The cutter used in this operation was known as Mexcut B. Prior to spraying a second coat of bitumen on the private driveway, Newton and his co-worker purged the lines with approximately 5 to 10 litres of Mexcut B. Following the purging of the lines Newton's co-worker suggested that Newton measure the contents of the tanker to check the remaining quantity of bitumen. In order to carry out the measurement of the remaining bitumen, Newton climbed up an access ladder at the rear of the tanker and opened the top hatch lid. He then withdrew a brass dipstick and recorded the dip measurement. He put the dipstick back in place and closed the top hatch lid, locking it tightly in place by hand. He stood up and prepared to walk to the rear access ladder when an explosion and fire occurred causing him to suffer burns. He ran towards the rear of the tanker and jumped to the ground. Workers from Tweed Heads Shire Council engaged in the roadwork activities immediately poured water over Newton's burns. Newton was conveyed by ambulance to Murwillumbah Hospital then transferred to the Burns Unit at Royal Brisbane Hospital for treatment of serious burns to approximately 40% of his body. 7 Mr Hannan's affidavit further particularised the way in which the case was advanced in accordance with the results of an investigation conducted by him. Those particulars stated : a. The practice of purging bitumen spraylines with cutter results in a small amount of cutter being forced into the bitumen tank. b. An explosive atmosphere was created by the following: - The cutter Mexcut B has a flashpoint at 61.5 degrees Celsius. - The bitumen tank temperature was between 140 and 150 degrees Celsius. - When the cutter Mexcut B was forced into the heated atmosphere of the bitumen tank with air it vaporised and formed a highly volatile gas. c. The top hatch lid seal packing was damaged and loose enabling metal to metal contact between the hatch lid and the tank top and allowing volatile gases to leak from the hatch. d. The most likely cause of ignition and the resultant explosion of the volatile gas was metal to metal contact occurring when Newton closed the top hatch lid due to part of the hatch lid seal being loose. e. At the time of accident Newton was wearing rubber soled steel capped safety boots, football socks, cotton underpants, cotton drill overalls, a polyester red safety jacket and personal spectacles. f. Inspection of Newton's overalls after the accident revealed that the overalls appeared to have been blown outwards by the explosion. g. Section 4.2 of the Code of Practice for Safe Handling of Bitumen Products (CP-20) issued by the Australian Institute of Petroleum Limited specifies that all personnel involved in the transport, handling, storage, blending, or spraying of bituminous products should receive training in the safe handling of those materials. h. Section 4.6.1 of the Code of Practice for Safe Handling of Bitumen Products (CP-20) issued by the Australian Institute of Petroleum Limited specifies the following minimum protective clothing wherever cutback bitumen is handled: - Approved eye protection, such as face shield or chemical goggles - Cotton overalls close fitting at the cuffs and overlapping the boots - Impervious gloves - Safety boots i. Newton did not receive any information, instruction, training or supervision from the defendant in the use of its bitumen spray tanker apart from being provided with the defendant's safety booklet to read. j. Following the accident the defendant modified the top hatch lid seal as follows: - diameter of lid increased to incorporate double width of seal around perimeter of lid - extension of steel plate ring at rear hinge side of hatch - rear screw adjustment at the rear of the hatch lid to enable an even sealing pressure to be attained. k. Following the accident the defendant's Occupational Health and Safety adviser recommended the following action in relation to the operation of bitumen spraying plant: - hatch seals to be checked whenever hatch is opened - tank dips to be taken prior to purging lines to ensure no person is in the hatch area when purging undertaken - hatch lid is to be lowered slowly and not dropped - all areas around bitumen tanker to be no smoking and tanker to be signed accordingly - tanker to be treated as flammable liquid transport - safety vests to be of non-static fabric - overalls to be of cotton drill and not synthetic fusible material - employees to be issued with reinforced plastic top cap safety boots - dip sticks to be located outside the hatch - hatch hinges to be towards truck cabin to avoid operator having to step over hatch l. Newton had been employed approximately 15 weeks by the defendant at the date of accident. Positions of the parties 8 Mr Brezniak in opening the case conceded that "no one until this time precisely identified or nearly precisely identified the source of the ignition of the flammable matter, the gas, but the prosecution does not rely upon proof of that kind." As counsel emphasised, "it relies upon the circumstances which gave rise to the presence of flammable gases leading to an accident which had these consequences"; here, "the consequences were rather serious 40 per cent of the body of Mr Newton was burnt". 9 It should immediately be observed that Mr J B Simpkins , counsel for the defendant, did not challenge the immediate circumstances leading to the incident nor the occurrence of the incident itself. Indeed, counsel made it plain that the necessary elements of the charges were accepted, other than that the prosecutor had made out to the requisite standard of proof beyond reasonable doubt that the detriment to Mr Newton's safety was caused by any act or omission of the defendant; and, so, the charges should be dismissed. In any event, Mr Simpkins put that because the same acts and omissions were relied upon for each charge then the prosecutor was only entitled to succeed, if any case be made out, upon one of the summonses but not both: see Boral Gas (NSW) Pty Ltd v Magill (1995) 37 NSWLR 150; (1995) 58 IR 363. 10 The defendant relied also on the defence available under s 53 of the Occupational Health and Safety Act in that no steps were capable of being taken by the defendant to avoid the risk unless the existence and nature thereof were known or able to be known - if there was any risk in the present case, but which was not conceded, it was something only able to be known upon reviewing matters of scientific debate and coming to a particular view about them so that it was impracticable to identify and attend to any risk. In reviewing the evidence led in the case, it is therefore helpful to have in mind the precise terms of s 53, as follows : 53 Defence It shall be a defence to any proceedings against a person for an offence against this Act or the regulations for the person to prove that: (a) it was not reasonably practicable for the person to comply with the provision of this Act or the regulations the breach of which constituted the offence, or (b) the commission of the offence was due to causes over which the person had no control and against the happening of which it was impracticable for the person to make provision. 11 The proceedings were vigorously contested by both parties. The prosecution called eight witnesses, including an expert witness, to support the case as framed and the defendant relied upon one expert witness in answer to the technical scientific evidence led for the prosecution. It was in the area of the expert evidence where much of the controversy between the parties developed, involving nearly 11 of the 13 days to hear the whole proceedings. 12 I have to say, as will become apparent from my reasoning, that I have found the bulk of the expert evidence, principally that given during cross-examination and which required so much hearing time, was of little assistance in furthering a determination of the subject charges. Effectively, that evidence was directed to the causa causans as the immediate reason for the explosion itself rather than what I see to be the relevant approach here as requiring attention to the causa sine qua non as the mix of existing factors but for which the direct cause could not have become operative and so the explosion would not have occurred. In other words, it seems to me, the bulk of attention focused on the accident per se instead of on the identified detriments to safety which were the subject of the two charges. It is true, as Mr Simpkins said, that it is necessary for a causal relationship to be established linking the defendant to the safety detriments in order for the charges to be made out, but, in my view of the expert evidence, it was taken to extreme and unnecessary lengths coming down, in may be said, to an academic review of applied scientific theory. I think that is to be regretted, however interesting the excursion was, because it tended to have the effect of distracting attention from the real inquiry under s 15 to become, erroneously, a review limited to the incident of the explosion itself. Nature of the offence created by section 15 13 The gist of the offence created by s 15 of the Occupational Health and Safety Act is the employer's failure to ensure health, safety and welfare in the workplace of his employees; that is, in my view, to so conduct the workplace that by some act or omission of the employer an identifiable risk to the safety of the employer's employees is thereby created. As the former Industrial Commission in Court Session ( McMahon DP, Hill and Hungerford JJ) in State Rail Authority of New South Wales v Dawson [1990] 37 IR 110), in adopting the observations made by Grove J in McMartin v The Broken Hill Proprietary Company Limited (unreported, Supreme Court 86/20002, 5 February 1988) that "it is necessary that a causal nexus be shown between such a breach and the fact of detriment to safety", remarked (at pp 120-121): Although s 15(1) creates an absolute liability on the employer, it is still nevertheless necessary for the informant to prove, according to the criminal standard of beyond reasonable doubt, that the employer failed to meet the obligation cast on him by the section. In other words, the mere fact that an accident occurs involving an employee, but without more, does not establish any liability in the employer; and that is so unless some causal nexus be established between the breach of statutory duty and the detriment occasioned to the employee. 14 This aspect as to the nature and breadth of the liability created by s 15 (like ss 16 and 17 of the Occupational Health and Safety Act ) has been authoritatively considered in the cases over quite some years. In Haynes v C I & D Manufacturing Pty Limited (1994) 60 IR 149, a Full Court ( Bauer, Hungerford and Cullen JJ) of the former Industrial Court was required on appeal to review a finding of not guilty to charges brought under ss 15 and 16 and expressed the view that the trial judge emphasised too much the accident itself as the relevant detriment to safety. Their Honours said (at p 157) : Sections 15 and 16 of the OHS Act are both concerned with failures to ensure the health and safety of persons at workplaces in terms inter alia of "risks" thereto; thus, the sections, even absent any actual accident causing death or bodily injury, nevertheless comprehend the commission of an offence where the relevant "detriment to safety" (as spoken of in Dawson and McMartin ) is but a risk, or, in other words, where the circumstances are such that an employer's act or omission has created a situation of potential danger to the health and safety of persons at his workplace. The OHS Act, as its long title indicates, has the prime purpose "(t)o secure the health, safety and welfare of persons at work" and that stated purpose may only reasonable be achieved, it seems to us, by construing the general duties or obligations cast on employers by Div 1 of Pt 3 thereof (which contains ss 15 and 16) as both preventive and remedial in nature, that is, both before and after the occurrence of an actual accident. 15 The point may be illustrated by reference to Rech v F M Hire Pty Limited (1998) 83 IR 293 where the Court ( per Hungerford J) considered prosecutions pursuant to ss 15(1) and 16(1) of the Occupational Health and Safety Act after a person suffered fatal injuries on being crushed beneath a forklift truck when it fell over the unfenced edge of a passageway onto an adjacent roadway. The question of a causal connection of the relevant employer to the detriment to safety necessarily arose for consideration. It was held in that case (at pp 317-318) that "the detriment was the absence of a guard rail along the edge of the passageway and the risks to health and safety thereby occasioned from persons and vehicles, such as forklifts, falling over the edge of the passageway" so that the central element of the offence had been made out because "the subject passageway … should have had an adequate guard rail erected along the length of its edge with the adjacent roadway in order to ensure the health and safety of persons against the risk of themselves or a vehicle, such as a forklift, falling over the edge of the passageway". As to the particular significance of the accident itself, it was then observed (at p 318) that "the accident concerned manifests quite markedly the nature and extent of the failure to ensure against such risks". 16 A Full Bench ( Wright J, President, and Walton J, Vice-President, with whom Peterson J agreed) of the Court in Drake Personnel Ltd, t/as Drake Industrial v WorkCover Authority of New South Wales (Inspector Ch'ng) (1999) 90 IR 432 at 453) adopted as a correct statement of law and principle in relation to s 15 the reasoning as above-stated in McMartin, Dawson and Haynes . In doing so, their Honours added (at p 453) "the observation that an offence under s 15(1) is constituted by the failure to ensure that employees are not exposed to risks, rather than the failure to prevent a particular accident". In referring to Haynes , their Honours directly put the position in the following way at (p 452) : The general duties created by the OH&S Act are directed at obviating "risks" to the health, safety and welfare of persons in the workplace … . The occurrence of an accident and the sustaining of injuries by an employee will certainly represent relevant evidence of the existence of a risk to the health and safey of employees and the seriousness of that risk. However, it is not the accident itself which constitutes the offence, but rather the failure of the employer to ensure that its employees are not exposed to risks while at work. 17 To a similar effect, in WorkCover Authority of NSW (Inspector Ankucic) v McDonald's Australia Limited (unreported, Walton J, Vice-President, IRC98/1104 and 1106, 4 February 2000) a person was electrocuted while cleaning kitchen equipment and his Honour said as to the causal nexus with the relevant detriment to safety the subject of the charges (at pp 112-113) : Section 17, like ss 15 and 16, requires that the liability of the employer be established by an examination as to whether there is a causal nexus between the breach of statutory duty and the detriment occasioned to the employee and not, as appears to be at least implicit in the defendants submission, by attention being given to the relationship between the conduct of the defendants and the actual accident or hazard that caused the fatality … The break in time between the movement of the grill and the cleaning operation and electrocution does not break the causal nexus in relation to the offence. The detriment to safety was occasioned by the failure to ensure the disconnection of power before the cleaning operation commenced or steps necesssary to be taken in preparation thereof. 18 Having in mind the defendant's approach in the present case by arguing the lack of a causal connection by reference to the incident affecting Mr Newton, that is the explosion (or fireball), I think it both timely and appropriate to refer to what I see to be the rationale for the approach to the vice to which s 15, and hence s 16, of the Occupational Health and Safety Act is directed. That was done by me in Kirkby v A & M I Hanson Pty Limited (1994) 55 IR 40 at 49-50 and I repeat it as follows : I think it notorious that workplaces have the potential to be unsafe and building sites, by their inherent nature, are certainly no exception. It may be undoubted, it seems to me, that the legislature had that in mind in enacting the Occupational Health and Safety Act which, as its long title states, has the purpose "to secure the health, safety and welfare of persons at work"; the objects of that Act in s 15(1) emphasise the point. And, so, Div 1 - General Duties of Pt 3, which includes s 16(1), of the Occupational Health and Safety Act was passed to effect the apparent purpose by creating absolute obligations on the relevant persons to remedy and protect against the perceived mischief of risks to health, safety and welfare in the workplace. Section 16(1) forms part of that statutory purpose and, I think, represents an instance of the legislature's concern to improve safety in the working environment. The High Court (Mason, Wilson, Brennan and Dawson JJ, with whom Gibbs CJ agreed) observed in McLean v Tedman (1985) 155 CLR 306 at 313: "Accident prevention is unquestionably one of the modern responsibilities of an employer." The approach was furthered by Mason, Wilson and Dawson JJ when their Honours said in Bankstown Foundry Pty Limited v Braistina (1986) 160 CLR 301 at 309: "In so far as legislative requirements touching industrial safety have become more demanding upon employers, this must have its impact on community expectations of the reasonably prudent employer". It is my view that the nature of the duties, and hence the question of whether an employer has offended against s 16(1), are to be construed in that context. As was stated by Lord Shaw in Butler v Fife Coal Co [1912] AC 149 at 178-179: "The commanding principle in the construction of a statute passed to remedy the evils and to protect against the dangers which confront or threaten persons or classes of His Majesty's subjects is that, consistently with the actual language employed, the Act shall be interpreted in the sense favourable to making the remedy effective and the protection secure. This principle is sound and undeniable." Again, and to a similar effect, Isaacs J commented in Rice v Henley (1914) 19 CLR 19 at 22: "In interpreting an Act which is directed to guarding against accidents and to the preservation of human life I think one should endeavour to carry out the objects of the legislature as far as the language of the Act will reasonably permit." 19 I affirm the approach thus stated and propose to follow it in this case, supported as it is by a long line of consistent authority: see Hannah v Ricegrowers Co-operative Ltd (unreported, Fisher P, 90/88, 20 November 1990 at p 8); Independent Cargo & Wool Services Pty Limited v Mingare (unreported, Fisher P, Glynn and Peterson JJ, CT92/1041, 10 March 1994 at p 4); Tyler v Sydney Electricity [1993] 47 IR 1 at 5; Warman International Limited v WorkCover Authority of New South Wales (1998) 80 IR 326 at 341; Watson v Southern Asphalters Pty Ltd (1996) 83 IR 446 at 456; WorkCover Authority of New South Wales (Inspector Viesis) v Thiess Contractors Pty Ltd (1996) 85 IR 12 at 30; and WorkCover Authority of New South Wales (Inspector Dowling) v Overtop Pty Ltd (1998) 86 IR 319 at 332. Evidence for the prosecutor 20 The initial witness called by Mr Brezniak was the prosecutor, Mr Hannan. He confirmed his appointment as an inspector for the purposes of the Occupational Health and Safety Act and pursuant to which he investigated the circumstances of the subject incident following inspections on 18 and 23 November 1994 of the bitumen tanker involved; he visited the site at Blackneys Road on 31 January 1995. Mr Hannan then prepared a report dated 28 February 1995 detailing the dimensions and features of the tanker. As to the hatch lid on the top of the tanker, he reported that it "was hinged to open towards back end of tank" and that "at the time of my inspection I was informed that the lid had been modified after the accident to accommodate 2 x 12 mm square wide seals"; he noted that "The dip stick is located under the hatch lid adjacent to the hatch lid total hold down hand screw … The dip stick is located inside the tank … A fabricated perforated mild steel box that fits into the hatch neck to prevent objects falling into the tank". Mr Hannan further noted the production to him by a representative of the defendant of "a pair of torn overalls said to be cut from the injured person by the ambulance staff … grey in colour … cotton drill … a red shrivelled up safety vest which he again stated was cut from the injured person. The red vest appeared to be of a polyester material … The boots taken from the injured person were steel capped … Leather upper, non leather lining, oil and acid resistant". Finally, Mr Hannan noted the presence at Blackneys Road of "overhead powerline 9.5 metres from the centre line of the road and estimated 6 metres from ground level … The area was well ventilated. The area was clear of any potential ignition sources". 21 Mr Hannan drew a sketch plan of the site showing the roadways, position of the bitumen tanker thereon, adjacent features (including the overhead power lines) and location of personnel at the time; he also took photographs of the tanker on 21 and 23 November 1994 showing its various pieces of equipment, including the rear, top walkway and hatch of the tanker. The modifications said to be made to the hatch seal and lid were plainly visible from the photographs due to the lack of discolouration from bitumen and from the effects of the fire which had occurred. 22 The Roads and Traffic Authority inspected the tanker concerned on 25, 26, 27 and 28 October 1994 and through Mr Hannan an inspection report on the bitumen sprayer dated 28 October 1994 was admitted into evidence. The report disclosed satisfaction of the tanker with the performance requirements for mechanical sprayers of bituminous materials, including as to the construction of the tank, overflow pipe, baffles, draw-off, circulation, tank heating tubes, dipstick and guide, burners, bitumen pump and hoses, spray bar, bar flushing and spray nozzles. The capacity of the tanker was shown as 12,150 litres. 23 Mr Anolek gave evidence for the prosecution. He had been employed by the defendant for about 9 years and on the day of the incident he was working as a bitumen spray tanker driver with Mr Newton as his operator at Stokers Siding carrying out road surfacing operations. It transpired that the work had commenced early in the morning and towards the end of the day, about 5.00 pm, the tanker was parked in the cul-de-sac off Blackneys Road after spraying portions of the roadway. What occurred was described in the following way by Mr Anolek in his evidence-in-chief : Q. Can you go back and tell the Court what happened that day? A. We were sitting in the cab of the truck and I asked Kevin, we were waiting for the sprayer tractors to put the metal over - we could not get over where we were, and we were going back to the right because I had the sprayer all lined up and when I was spraying downwind, so that might be the way to deal with the cutter and spray back up till it locks us into the area we were in. We had come up spraying, we would turn and spray that and we blew the bars and pulled into the gate and were sitting waiting for the guys to cover it and we were sitting in the front talking and I said to Kevin, "All right if I do my paper work? You reckon you can save me a dip when we get back to the depot?" He said, "Yep, right." He climbed out of the passenger's side, went around to the back, climbed up the back of the truck up to the top. I watched him climb onto the back of the truck and I watched him take the dip through the rear view mirror. He told me the dip. Then I took my eyes off him and I was working on my books sort of thing at the time and next thing there was a loud noise and a large flame that came out fast over the truck where I was sitting, over the top of the cab and was rising and it was reddish in colour and it lasted about two seconds and it was all over, the heat and the smoke. Then I heard Kevin screaming at the back of the truck. I jumped out of the truck and went to his aid to see, to get him to water. I raced him around a house trying to find a tap to cool him down and we did not find the tap straight away and we got some of the guys to get their drinking bottles and put his hands in cups of water to cool him down and we found the hose up the back and we were sprinkling him with water to cool him down. I could not do more to help and I went up and had a look. There was a small spot fire burning, so I got the fire extinguisher and put the fire out. I got that out and we called the ambulance. Q. After the incident, did you measure the temperature of the tanker? A. I had a look after, I just had a look at the temperature and it was showing 145 I think if I remember. … Q. Did you see whether Kevin had any gloves on when he went up there? A. I did not see. Q. Did you see whether he had eye protection? A. He had his glasses on. Q. Personal glasses? A. Just his personal glasses. Q. What sort of boots did he have? A. Steel-capped leather workboots with leather soles. Q. What about clothes? A. Heavy drill cotton overalls and he had a nylon red vest on over the overalls. Q. You say you climbed onto the tanker? A. Yes. Q. After the accident? A. Yes, there was a small spot fire. Q. Did you see anything burning around the hatch cover? A. It looks like it has blown out and it was landing up on top. Q. When the event occurred, when you heard the sound and saw the flame I think you said it was, were you smoking? A. No I was not. Q. Do you know whether Kevin was smoking? A. I did not see him smoking. … Q. Has there been any change since that day in relation to procedure? A. Well, we have been told since we must wear a mask, a helmet with a mask, eye protection and rubber gloves as well as our overall, boots which we normally wear. Q. What about the practice in relation to measuring the contents of the tank? Any change in that? A. I believe there was a notice came out to say that we should dip before we blow the bars. Q. Is that happening now? A. Yes. Q. So when are you dipping now in time? A. In time? Q. After you blow the bars? A. Before we blow the bars now. Q. Any other changes? A. Not that I can think of, no. 24 Mr Anolek explained that about 5 minutes before Mr Newton went to the tanker top to measure the amount of remaining bitumen that they had "blown the bars" - that process, it seems, was performed from time-to-time to clean the spray bars located at the rear of the tanker of adherent bitumen so as to enable effective spraying from the bars. The process involved, as Mr Anolek agreed, "isolating the spray bar from the taps and draining or blowing the cutter through the spray bar"; he added, "You actually open the taps up as well and so kerosene comes out of the taps and it cleans the bitumen from the little nozzles … to keep it clean". He said that during this process some of the cutter "goes back into the tank" and mixes with the bitumen. Apparently, during the bitumen spraying work cycle the tanker is dipped to measure its contents typically 20 times a day. Mr Anolek said that after spraying the tank is dipped but "I don't think it matters" whether the bars are blown before or after the tank is dipped. He said that after the bars were blown here there was no further spraying before Mr Newton dipped the tank. 25 Apart from the use of the "cutter" (a mixture of kerosene known as Mexcut B) to clean the spray bars, cutter also was used in this case in the operation by mixing it with the bitumen in the tank to prevent the bitumen cooling on the road too soon during the spraying phase; thus, as Mr Anolek said, "if it is a really cold day you put in more cutter and heat up". The amount of cutter injected into the tank was calculated as 3 per cent by volume of the cold bitumen so that it was necessary to measure the contents of the tanker before the introduction of the cutter; that process occurred in the present instance. 26 After saying that Mr Newton knew how to dip the tank because he had worked with him for about 12 months, even though no training course was given, Mr Anolek gave the following evidence as to training received in the operation of the tanker and what dangers existed : Q. Have you attended any lessons in how to operate the tanker and what the dangers are? A. It has been an ongoing thing from people, being shown by people who know how to use those machines. Qualified people. Who I classify as qualified. There is a lot to learn on these things and you treat them with care. … Q. Are there risks you are aware of that you have been told about? A. Yes. Q. What were the risks that you were told about before 17 November 1994? A. You don't smoke around them. That is one of the main things. When you light your lamps you don't leave your lamps burning. When you are spraying you don't light your lamps if there is any bitumen in the machine or it could explode. If you are sucking cutter in you have to put water testing paste on and drip that in because it has a heater in there which could create an explosion. You don't have naked flames around. You try not to park under powerlines, to dip your tank. That is pretty much about it. Q. Anything about dipping the tank apart from not parking under powerlines? A. No, I don't know anything of that sort. You have to dip the tank. You have to know how much you have left in there. You have to dip it. Q. In particular, directions, guidelines or published material, you know printed material, concerning any dangers in connection with vapour that comes out of the tank? A. Mainly just yes, not to smoke around the area and be careful of naked flames. Considering you have to heat your bar up with a gas lamp, so you can be around the back of the truck. Me myself I would not have my pump circulating. I would heat it up first and put it in before I circulated. I would not have it sucking in because that creates flames, which being gas, you need to watch all these things. You have to be very careful and we try to be. Q. Any instructions or guidance about the danger of inhaling or breathing any fumes from the tope of the tank when the hatch is open? A. No. Q. Any information or instruction or training in connection with the chances of the explosion when the hatch on the top of the tank is open, apart from not having a lighter or cigarette with you at the time? A. Well no, not really. … Q. … The question was was there any training, any instruction, any information given to you at all about the difference in vapour? A. No. Q. There was not. You understand? A. Yes. Q. Lastly on that matter, any instruction, information or training as to whether dipping inside the tanker, dipping as you did, should be carried on differently after you had blown the bars? A. No. 27 During the cross-examination of Mr Anolek, Mr Simpkins concentrated on the use of cutter to mix with the bitumen to prevent cooling and for cleaning the spray bars as being part of the ordinary and usual operational process followed over some years. In stating that Mr Newtown called to him from the top of the tanker after the dip was taken that the amount of bitumen remaining was 1,700 litres, Mr Anolek agreed that that quantity of bitumen within the unit when blowing the bars of the spray unit was "common place" and that he had never "experience(d) anything like an explosion or flash ignition following on an ordinary blowing of the bars"; indeed, Mr Anolek agreed he had never heard of that happening. Evidence was then given by Mr Anolek of his observations when Mr Newton was on the top of the tanker, to this effect : Q. He was on the top of the truck and you had a side mirror and you could look through and see him on the top? A. I could see that. Q. You looked at the mirror at the time. You could not speak to him? A. I was watching him through the mirror, yes. Q. After he gave you a figure of 1700 litres, you turned back to your paper work? A. That is right. Q. The next thing you observed was a noise? A. Very loud hissing, swishy type noise. That noise and then a flame, virtually instantly. Q. Was that a kind of noise you had ever heard? A. Never. Q. Never in your work as an operator or assistant operator of a bitumen spraying truck? A. No. … Q. Was it then you saw the flames you have described? A. Yes. Q. I think you told his Honour those flames seemed to last a second or two? A. Yes. Q. Then there was some smoke? A. Yes. … Q. How long was it after the accident that you went back to the spraying unit to try and work out what state it was in and what had happened? A. Three, four, five minutes maybe. Q. You went to the top of the truck? A. Yes. Q. I think you told us there was a small fire there? A. Yes. Q: What was it that was on fire? A. The packing from around the hatch cover was laying on around the hatch and it was burning and there was a couple of pieces of cotton waste which we had been using to wipe the dip stick with that were burning. Q. You then at that time decided to see whether it was sealed? A. No, I did not touch the hatch. All I did was look at it and seen it was closed and sealed, it was locked in. Q. You made certain yourself the hatch had been closed? A. The hatched was closed and the latch wound down, yes. Q. Did you look at the spray unit for signs of damage which might give some origin of the fire or flame? A. I took the temperature and it was 145 I recollect. I also looked under the vehicle to see if there were any scorch marks apparent through where the overflow pipe came out and I was looking for scorch marks on the ground because it shut down and there was nothing there. Prior to that I had a fire extinguisher on the top of the truck and put those two small spot fires out so there was a fair bit of white powder about from the fire extinguisher and I could not see any other damage. I could not see any damage other than the packing around the edges of the hatch that was burning. 28 The injured employee, Mr Newton, gave the following evidence as to what occurred on 17 November 1994 at Blackneys Road : Q. What happened on that day? A. We went to Stokers Siding and we were there to spray Blackneys Road and as the day went on - we started to proceed to spray; and as the day went on, went later later of course, and then we got to do some private driveways, and I can't quite remember the name of the people whose property were on. Anyway, the truck, we ran out of bitumen in the tank of the truck. We had to go and refill at the end. At the end of the tank you always take a dip to see how much was left. I had cleaned the bars. … Q. Now just before you continue, is cleaning the bar, the same as blowing the bar? A. Yes. Q. You had blown the bar? A. Blown the bar, yes. Q. What happened then? Q. I climbed up the back of the truck onto the top of the truck. I opened the hatch cover and proceeded to take the dip. After I took the dip, I close the hatch cover over and I stood up, turned around to walk off the back of the truck and then I was engulfed in flames, and then sort of ran for me life, basically jumped off the back of the truck, hit the road and then took off again. Q. As a result of that experience you had been in hospital for quite sometime, weren't you? A. Yes. Q. And you had sustained certain permanent injuries made to your skin, hadn't you? A. Yes. Q. You had skin grafts? A. Yes. … Q. It was you, it was not Mr Anolek who blew the bar? A. No, it was me. Q. Do you know how much Mexcut, that's the cut you were using, that you put through the bar to clean it? A. Probably two or three litres. Q. Or more? A. Or it could have been a little bit more. … Q. When you did that, did you do any more bitumening, that is laying of bitumen before ascending the tanker? A. No. … Q. Was that the next thing you did? A. I went to the dip, that's the very next thing I did. Q. Why did you do a dip then? A. Wayne asked me to do it as we were busy, he was doing the bookwork at that time and I was there, I was on the back of the truck. I was just asked to do it. … Q. Coming back to 17 November 1994, did you obtain a reading from the measurement using the dipstick? A. Yes. Q. What was that? A. My memory it was about seven, eight hundred litres. Q. Did you say anything to Mr Anolek about what reading you obtained? A. Yes. Q. What did you say? A. I yelled out over the side of the truck to Wayne in the cab that it was seven, eight hundred litres. … Q. And you then put the dipstick into the receptacle, or withdrew it from a hole in which it then was? A. I withdrew it from the hole and had a bit of cotton waste cloth and wipe the dip, the dipstick, clean and put it back in and withdrew again to see how much was left. Q. Did you after completing the task and telling Mr Anolek what reading you observed did you fasten down the hatch again? A. Yes. Q. Are you sure of that? A. Yes. Q. And did you as best you can remember take any steps, or make any real movements towards the rear of the tanker? A. I then - you know, I think I made one or two steps before I was engulfed. Q. You were smoking? A. No. … Q. On the 17 November 1994, on the day that you were injured, were you able to smell when you were on top of the truck, any fumes at all? A. Yes. … Q. I want to again take you back to the day you were on top of the tanker before you were injured. Did you notice anything about the hatch cover before you closed it? A. Yes. Actually when I opened it up a bit of hatch packing had fallen out. Well not so as much was fallen out was hanging by a thread. It had worn out on one end and was just hanging by the other end, probable six or eight inches of it was. Being up at Tweed no tools, nothing to fix it with, all I could do was poke it back in, back into the slot where it was and close the hatch. Q. When you closed the hatch before you were engulfed by heat, did you see any of the seal that you referred to as hanging loose protruding? A. Not that I can remember. Q. Were you ever told during your employment with Boral Asphalt that there was a danger attached to breathing in the fumes which you say you noticed? A. No. Q. Did you breath in the fumes at any time? A. I couldn't avoid it they were every where. 29 During the process of the cleaning of the spray bars with cutter, Mr Newton denied under cross-examination that any residue was pumped back into the container and said that "It's actually sucked back into the tank of the truck, not pumped back into the container. … where all the rest of the bitumen is." 30 As to protective clothing worn at the time of the explosion, Mr Newton confirmed he was wearing cotton drill overalls, steel-capped safety boots, red safety vest and spectacles; he was not wearing gloves nor any other protective covering over his hands nor did he have any other cover over his face or eyes. 31 Although Mr Newton had used the dipstick to measure the level of bitumen in the tanker on some three or four occasions, he said he was told by the defendant that that task was part of the driver's job and not his as the operator. As to training given to him to dip the tank, he said in evidence : Q. Were you given any training in what was required to do when you went over to put the dip down? A. Very little training, sort of, like, you stand on the ground and you watch from the ground and you never actually got up there with anyone to do it who got to show you. You just stood on the ground and watched them from the ground. Q. Apart from seeing it done, were you given any classes, any lessons, in how to do it? A. No. … Q. How long prior to that date, 17 November, had you commenced employment with Boral Asphalt? A. I started with Boral Asphalt on 15/8/94, so it was only a few months. Q. When you started working at Boral Asphalt what sort of work did you start doing? A. Basically we were - we started straightaway each. There were three of us employed all at the same time, within a couple of weeks. We were all basically started out as an operator to learn how to do all the bar work at the back end of the truck. Q. You also had been a broom user? A. Yes. Q. You had been a traffic controller? A. Yes. Q. And you had been a spray operator? A. Yes. Q. Now in none of those duties were you required as part of your duties ordinarily to ascend the tanker and look into the hatch? A. No. … Q. Were you given any instructions about what occasions you were to use the gloves? A. Yes, we had instructions to use the gloves when you were folding at the bars, or anything that really to do with the back of the truck because everything is so hot and everything is about 170, 180 degrees at the back of the truck, but that was it. Q. What about the opening, closing and use of the dipstick from the hatch on top of the tanker, were you told to wear gloves on those occasions? A. No, there was no mention of wearing gloves on the top of the truck, no one ever did. So there was no mention, no one said to me: "You have got to wear gloves", or "You do not have to wear gloves". It was just no one ever did. Q. Were you told at any time about any danger from fumes coming out of the top of the tank through the hatch? A. No, not at any time. Q. And this is not at any time since you started there? A. That's correct. … Q. Now, Mr Newton, did you yourself seek, and were you provided with, any guideline in writing, any information in writing as to the steps to be taken when measuring with dipstick what was in the tank? A. No. Q. You had never seen anything? A. No. … Q. Can you tell the court what you remember you did do as part of what you say was identified as an induction? A. Well, it was sort of like when you had a fair ten minutes, or fifteen minutes, I was called into the office. I think that's Graham Skidmore. I am not sure. I think his name was Graham Skidmore who was there. He called me into the office. He just there read a few things to you, asked you a couple questions. That was it. Signed a bit of paper you were inducted. That was basically it. … Q. Were you given any lessons in what personal protective equipment to wear? A. No. Q. Was anything said to you about what was in the Occupational Health and safety handbook about which you have given evidence? A. No. Q. Were you asked whether you understood that you received induction training? A. I can't remember. Like I could have been out on the road for 10 hours that day when they called me in for 10 minutes. 32 Under cross-examination, Mr Newton gave the following further evidence as to training and instruction on-the-job : Q. Apart from whatever may have taken place in the depot with the RTA inspectors present, may I take it that one of them certainly did occur when you got out with a hot load assisting a driver of the spraying unit, was that you were given from time to time advice on instruction by the experienced operator that you were put with? A. Yes. Q. But that advice you say was essentially about other aspects of the job than the dipping at the top of the truck? A. Yes. Q. The position though that you had reached by about November 1994 in respect of all of those other aspects, apart from the dipping which I will come to, was that you regarded yourself as being a competent and efficient operator because of the on-the-job training and instruction in the unit? A. Yes. 33 During the course of Mr Newton's evidence, a booklet produced by the defendant entitled "Boral Asphalt - Safety Handbook, Road Surfacing Division" was admitted into evidence. Section 7 of the booklet dealt with spray sealing and in para 7.1 it was noted that "Kerosene vapours are highly flammable and explosive. During 'cutting' operations all flames and sources of sparks (static electricity) must be eliminated". Mr Newton agreed that the defendant had issued him with the safety handbook and he had read it. 34 A truck driver employed by the Tweed Shire Council, Rodney Keith Harper, was standing about 20 to 30 feet away from the front of the bitumen tanker when the incident occurred to Mr Newton. He first saw Mr Newton on top of the truck dipping the tank and saw him close the hatch lid before he turned away to carry on a conversation. On hearing the noise of flame, Mr Harper (with Mr Anolek) provided assistance to Mr Newton by hosing him with water. Mr Harper did say, however, that what attracted his attention to look towards the tanker was when he heard "a whooshing noise with this small - it was not small - explosion, it never had a real lot of noise". 35 The defendant's occupational health and safety adviser, Graham Skidmore, and who was so employed in November 1994, gave evidence for the prosecution. Mr Skidmore as part of his duties enquired into the incident involving Mr Newton and made a number of recommendations to the defendant for certain corrective action to be taken, as follows : - Hatch seals are to be checked whenever hatch is opened - Dip is to be taken prior to flushing lines to ensure no person is in the hatch area when flushing is undertaken - The hatch lid is to be lowered slowly NOT dropped - All areas around bitumen tanker to be declared mandatory NO SMOKING and tanker to be signed accordingly - The tanker to be treated as FLAMMABLE LIQUID TRANSPORT - Safety vests to be of non static fabric - Overalls to be cotton drill not synthetic fusible material - Employees to be issued with reinforced plastic toe cap safety boots - Dip sticks to be located outside the hatch - Hatch hinges to be towards the truck cab to enable the operator to close the hatch and move away without having to step over the hatch 36 Although it was common ground that Mr Skidmore was not an expert witness on the cause of the explosion, counsel agreed that the terms of his report, called a "Critical Incident Report", on how he came to make the recommendations should be admitted into evidence for that limited purpose. In that respect, the report stated: Cause The source of ignition has not been positively identified, however the cause of creation of an explosive atmosphere within the tank has been established. The current practice of "blowing the bars" or purging the lines to remove bitumen residue is to force cutter (in this case Mexcut B) through the lines with the bitumen pump at approximately 50 psi. This will purge all lines with some cutter exiting through the sprayers and a small amount forcing into the bitumen tank. It is to be noted that only 5-8 litres of Mexcut B is used for this purpose. The explosive atmosphere was created by: - Mexcut B has a flashpoint at > 61.5c - The tanker temperature was between 140c - 150c - The mexcut B when forced into the heated atmosphere of the tank with air vaporised and formed a highly volatile gas. The short term of the explosion being about one second is consistent with the small amount of mexcut B entering the tank. As stated the ignition source is not positively identified however could have come from metal to metal due to part of the hatch seal being missing or by a discarded cigarette, the most probable being metal to metal contact. Investigation Investigation into the incident eliminated any ignition sources close to the sprayer including, fires, exhaust hot spots, faulty electrical system, mechanical hot spots, sparks created by damaged steel toe caps on boots, other vehicles, electrical wires and electric fence. - Static electricity from clothing was eliminated as injured was wearing cotton drill overalls. - Burner tubes were inspected for internal hot spots. The conclusion was reached the most probable cause being metal to metal contact due to damaged hatch gasket permitting hatch cover to contract hatch rim on tanker. 37 Regarding the above recommendations for the tank to be dipped prior to cleaning the bars, dipsticks to be located outside the hatch and the hatch hinges to be moved, Mr Skidmore indicated the rationale in the following way : Q. Do you offer to the court now any explanation for that recommendation? A. Certainly. The reason for that was because we assumed and I would like to qualify also I am not an expert, is we assumed that the volatile atmosphere was created when the cutter was injected into the tank. The intention of that recommendation was to ensure that the dip was taken before the additive or the mexcut or cutter was added so there was no possibility of there being an explosive atmosphere there when it was taken. Q. Stopping there, you know the bitumen which is in the tank is in the tank ordinarily with kerosene? A. Yes. Q. You are not suggesting that practice ceased? A. No. Q. You are suggesting that the practice ceased in those circumstances, are you? A. Yes. Q. Why? A. The assumption was when the cutter, after the flushing was done the cutter would go back into the tank and if the tank was heated to a fairly high degree of course it would create that gaseous atmosphere. The idea was to have the dip taken before flushing so the possibility of a gassy atmosphere being created - the dip would be taken before there was the possibility of that gaseous atmosphere being created. Q. Do you say that step would reduce the danger? A. Yes I believe it would. It would not have a person in that area. You would not be exposed to danger, yes. … Q. The next of the recommendations which I wish to take you to is your suggestion dipsticks be located outside the hatch? A. Yes. Q. Can you tell the court why you recommend that? A. Yes, it would prevent the necessity to open the hatch and to have exposure to the vapours and it would be merely put through a small aperture, much the same as a dip in the service station in the ground where they have a small aperture, put the dipstick out and put it back through so the person would not be exposed. Q. What is the danger, by being exposed to vapours? A. So there is no possibility of the vapours and an explosion as we saw. Q. Lastly, on the recommendations which you made you suggested the hatch hinge be towards the truck cab to enable the operator to close the hatch without stepping over the hatch. Why did you recommend that? A. When we looked at the operation we were trying to establish how a spark occurred and one of the ideas we had was it could possibly be metal to metal contact from the edge of the hatch, striking the hatch. If the hatch was not sealed properly it would be compressed by someone standing on it as they were getting away and perhaps again creating a spark by just the friction of metal on metal. So it was just another idea, going, as I said, to the nth degree, that would remove any possibility of a spark being created. … Q. At the time you came to produce the Critical Incident Report I think you told us a moment ago the view you had reached after speaking others was the introduction of cutter during the blowing of the bars process had given rise to a volatile explosive atmosphere within the tank spraying unit? A. Yes. Q. It is correct to say all the recommendations you came to make in that Critical Incident Report proceeded upon that state of mind? A. That is true. Q. And your recommendations were designed to attend to that risk? A. Yes. 38 Following the incident on 17 November 1994, the defendant arranged for Graeme McKenzie, a partner in the firm of David Ardill & Associates Pty Limited, a consulting engineer specialising in structural engineering, to inspect the tanker involved for possible damage to its shell. Mr McKenzie inspected the tanker on 18 and 21 November 1994 on instructions from the defendant and observed, as he said in his report dated 21 November 1994, "the explosion occurred after the top inspection hatch had been closed, causing a flash of ignited vapour to blow out through the seal at the rear side of the hatch". As to the inspection on 18 November 1994, Mr McKenzie inspected the top access hatch and noted "that the seal around the perimeter of the lid had been replaced with a similar seal to that which had been installed at the time of the explosion. It was noted that this seal was approximately 12mm which provided only minimal tolerance for non-metal-to-metal contact between the lid and the tanks flange during closing." As to the inspection on 21 November 1994, Mr McKenzie noted in his report that "The lid to the top access hatch had been modified to incorporate … a double width of seal around the perimeter of the lid … an extension of the steel plate ring at the rear ('hinge' side) of the hatch … a rear screw adjustment at the rear of the lid to enable an even sealing pressure to be obtained". 39 William Franklin Brown, a supervisor employed by the defendant at its Lismore depot for about 3 years, had responsibility for the bitumen spray tanker involved in the subject incident. He said in evidence that following inquiries the defendant considered a number of suggestions for changed work practices in the operation of the tanker but the procedure was still the same as before the explosion. Mr Brown under cross-examination gave the following evidence as to the particular training given to Mr Newton : Q. Can you tell his Honour what that training was? A. Most of the training is on the job, by qualified experienced people. They are also trained, if there is a spray certificate test to be done by the RTA, Kevin would have done at least one of those on the back of the sprayer - dipsticks, hatches - it's done time and time again over a minimum of three days the test goes for, using cold products where no danger occurs, to become familiar with spraying or handling emulsions which are cold products again. The new guy always goes with an experienced person on these types of jobs - always. That would lead them up to an operator on the hot bitumen sprayer. From there Kevin, we had got him his 3A licence on the truck with some intention down the track for him to be a sprayer driver and that would put him in the cab. That's how we all learn. Q. The process you have described of performing the cold test for the RTA, is that a process which occurs before or after a new employee is permitted to operate that hot work outside the depot? A. Always before. It is a necessary requirement as long as they have had a lot of instruction and they are always with an experienced and qualified operator. 40 It seems that Mr Brown visited the Blackneys Road site a day or so after the incident and gave the following evidence of his observations concerning whether the explosion was pressurised as being inside the tank or a fire in the open on top of the truck : Q. When you went out to the site of the accident did you locate the location or approximate location of the spraying unit at the time the accident occurred? A. Yes. Q. Did you examine the surface of the roadway? A. Yes. Q. What were you looking for when you did that? A. We were looking for a burn mark or pressure mark on the road, which was gravel, to determine whether the explosion was inside the tank and pressurised and blown out the overflow, or if it was just a fire on top of the truck. Q. When you went out and looked at the roadway, did you see any sign at all that the explosion had occurred within the tank of the spraying unit and expelled out on the surface of the roadway? A. We found nothing. 41 In 1990, the Australian Institute of Petroleum Limited first published a booklet entitled "Code of Practice for Safe Handling of Bitumen Products". The second edition published in June 1993 (AIP CP20-1993) was admitted into evidence in the prosecutor's case, without objection by the defendant. The Code represented a combined effort from the bitumen supplying companies, road authorities and user industry associations and covered various activities in the handling of bitumen and bitumen products, including transfer into receiving vessels (sprayers and on-site blending). Specifically, the Code was intended to cover the use of inter alia bitumen, cutback bitumen, cutting oils and their derivates, including adhesion agents and other additives. I accept that the Code had application to the circumstances of the present case where bitumen and cutter (Mexcut B) were used as part of the work process in spraying the roadways. 42 In dealing with its subject matter, the Code in Section 1 - Introduction noted "the need for a uniform code for the safe handling of bituminous products for hot sprayed works" and that "The handling of bituminous products can be hazardous to personnel. To ensure that the risks associated with such operations are properly managed, the development of safe standardised procedures, together with the training and education of personnel in this industry is essential". Whilst disclaiming an intention to replace individual organisations' codes or regulations, the Code provided, as its opening words said, "a set of minimum standards for safe handling of bituminous products". 43 Many sections of the Code are of present relevance. However, it is sufficient to cite some of its more directly significant provisions, as follows : 3.1 General The hazards that may arise during the handling of bitumen and related products are due to: (a) the high temperatures involved; (b) the flammable nature of some of the products; (c) the possible presence of toxic materials or vapours. Application of the guidelines in this Code is intended to eliminate the potential hazards that may arise due to these factors. However, an understanding of the hazards is desirable to ensure correct interpretation of the Code. … 3.3.2 Sources of ignition … (c) Carbonaceous deposits - excluding coke Carbonaceous deposits arise from the condensation of bitumen vapours on the underside of tank roofs or walls, or the thermal cracking of bitumen to form coke in high temperature areas such as around heater tubes. These deposits do not normally provide an ignition hazard unless they are disturbed, exposing underlying pyrophoric deposits to air. Pyrophoric metal oxides are formed from the reaction of the metal with oxygen. These deposits will self-heat when they are exposed to a sudden increase in temperature or oxygen supply arising from a change in storage tank operating conditions, such as an increase in temperature control settings, or the opening of manholes. In order to avoid self-heating and possible auto-ignition, carbonaceous deposits, once formed, should be kept in a steady state with their surroundings until such time as they can be removed by thorough tank cleaning. This steady state is promoted by: (i) avoiding through drafts of fresh air in tank vapour spaces, by keeping hatches closed, etc; (ii) avoiding step changes in temperatures surrounding the deposits. This includes avoiding the introduction of bitumen at higher than normal temperatures; (iii) removal of these deposits by cleaning before they begin to break away, exposing new surfaces at which self-heating might occur. … 4.2 Training All personnel involved in the transport, handling, storage, blending or spraying of bituminous products should receive training in the safe handling of these materials. This training should include instructions on the correct procedures for product handling including the operation of the equipment involved, the hazards involved, the wearing and use of protective clothing and equipment and procedures to follow in the case of an accident. In relation to road transport of cutback bitumens, both the vehicle owner and the contractor must be able to demonstrate that the vehicle driver has been trained in the following, in order to comply with statutory requirements: (a) the hazardous properties of the product being transported; (b) the actions to be taken, in order to comply with the ADG code; (c) the operation of all equipment on the vehicle; (d) the use of personal protective equipment, fire fighting equipment and product handling equipment such as pumps, burners and compressors; (e) actions to be taken in the event of an accident involving the vehicle; (f) routes to be followed when operating the vehicle. … 4.6.1 Protective clothing Where bitumen is handled as cutback or emulsion, the outer clothing worn should be designed to protect against splashes and avoid prolonged skin contact with the product. It should include: - approved eye protection, such as face shield or chemical goggles; - cotton overalls close-fitting at the cuffs and overlapping the boots; - impervious gloves; - safety boots. … 5.3.2 Blending of cutters and fluxes with bitumen in tank wagons and sprayers The main dangers associated with blending cutters, and fluxes with bitumen relate to the risk of fire or explosion and boilovers due to contamination of the products with water. The flammability hazard is greatest with cutters and the risk of contamination with water greatest with drum-stored cutters and fluxes. … (a) … (b) … (c) During blending, no source of ignition should be permitted within a distance of 15 metres of the operation. (d) … … 5.3.7 Conditions after discharge (a) Cleaning of pump internals, hoses and tank wagon pipework will be required after discharge of bitumen. Cleaning solvents should not be discharged into bitumen storage tanks. Instead, a separate solvent storage facility should be established, and connected to the discharge pipeline on the tanker side of the discharge valve. At the completion of discharge, a small quantity of solvent should be circulated through the tank wagon pipework. This solvent should be pumped or sucked back into the solvent storage tank or suitable storage vessel. (b) If air or inert gas pressure has been used to facilitate discharge, the tank wagon should be vented safely down to atmospheric pressure, using the tank vent, before the vehicle is dispatched. (c) A check should be made before departure that all hatches, covers and valves on the vehicle wagon are closed and secured in the closed position. … 7.3.6 Access to bitumen tank tops Access by personnel to hot bitumen tank tops should be strictly regulated at all times. It should be avoided as far as is reasonably practicable, during product movements into or out of the tank concerned. It should be prohibited : - during the blending of cutback; - during raising of the tank temperature; - during any outbreak of fire in the vicinity; - during periods of high wind; - during electric storms. 44 Pursuant to s 27 - Notification of accidents and other matters, of the Occupational Health and Safety Act , the defendant, by Mr William F Thompson as its Area Manager, submitted an Accident Report dated 21 November 1994 to the Workcover Authority notifying the present accident. The report contained the following answers to the questions posed therein : 24 What led up to the injury or dangerous occurrence? Newton was on top of Bitumen Tank checking Quantity. He closed the hatch and an explosion and fire occurred causing Newton to leap from the tank. 25 How exactly was the injury or dangerous occurrence caused? Fire escaped through the hatch and came into contact with Newton. 35 Give details of any action that has been, or can be, taken to prevent the accident from happening again. 1) Re-designed hatch cover to prevent metal to metal contact. 2) Provide Anti Static Electricity measure. 3) Engage consulting engineer to check tank for damage. 45 The evidence of the above witnesses called by Mr Brezniak completed the so-called lay or non-expert evidence in the proceedings. I have endeavoured to cite the primary and relevant aspects thereof having in mind the issues involved and the manner in which the case was argued. Essentially, there was little, if any, disagreement on the facts which emerged therefrom (except perhaps as to the amount of bitumen in the tank as measured by Mr Newton, either 700 to 800 litres as he said or 1700 as Mr Anolek said he heard Mr Newton call, and the degree of training and instruction given by the defendant to its employees, such as Mr Newton). Nevertheless, there was a sharp dispute between the parties as to the proper inferences which should be drawn from those facts as illustrated by the differing views expressed by each of the two expert witnesses concerning the reasons for and the cause of the explosion. I turn now to that material. Prosecutor's expert evidence 46 The WorkCover Authority asked Anthony Green to provide an expert opinion regarding the subject explosion on the bitumen spray tanker on 17 November 1994 and, in particular, to address its cause and origin, appropriate conditions for the operation of the spray tanker and any other issues deemed important. For that purpose, Dr Green questioned Mr Newton, Mr Anolek and the prosecuting inspector, Mr Hannan, and had access to certain documents provided by the WorkCover Authority. 47 Dr Green was then a senior lecturer in the Department of Safety Science of the University of New South Wales and his qualifications were a B Sc (Hons in Chemistry) and a Ph D; he had membership of a number of professional bodies and learned societies, including the Royal Society of Chemists, Combustion Institute (Australian New Zealand Section), International Association for Fire Safety Science and Research Committee for the Fire Code Reform Centre (Building Code of Australia). His experience spanned a period of 20 years as a specialist in explosion and fire phenomena while working in Australia and in the United Kingdom, covering research, policy and investigation of major hazards associated with industry and industry consultant and lecturer. In particular, he had conducted research over a broad spectrum of problems as to computer modelling of fires and explosions, experimental validation of computer models, fire and smoke spread, fire material properties, fire and explosion control systems, risk and hazard identification and assessment, development of operational risks analysis, development of experimental techniques and development of forensic investigation techniques. He had conducted at least 11 major investigations into fires and explosions since 1986, including a bitumen fire at Pinkenba, Qld in 1994 and two bitumen explosions at Mogo, NSW in 1993 and at Kemcor, Altona in Victoria in 1991. Dr Green had published widely, both on his own accord and with others, covering various aspects related to fires and explosions. Dr Green's qualifications and expertise were not the subject of challenge and, in my view, it may be accepted he was eminently qualified to give expert evidence for present purposes. 48 Dr Green's first report dated 14 March 1997 was admitted into evidence. In para 1.2 thereof, his opinion was summarised in the following way : 1.2 Summary 1) The fireball resulted from ignition of a substantial release of flammable vapour (less that 50 m3). 2) The cause of ignition being smoking by Mr Newton is inconsistent with Mr Harpers observation and with the position of full thickness burns on the hands, buttocks and legs. 3) Ignition could have been caused by any of the following: - pyrophoric material in or around the vent tube - exposed carbonaceous material around the heating pipes - Mr Anoleck ( sic ) smoking in the drivers cabin with the window down - an electrical fault on equipment particularly the pump motor - hot surface on the pump, brakes or exhaust - uncontrolled source near the house 4) The practice of pumping cutting fluid directly into the bitumen tank is in breach of Australian Institute of Petroleum Code of Practice for Handling Bitumen Products (CP-20,1990:section 5.3.7) 5) The practice of venting the bitumen tank which is used for containing bitumen cutter mixes creates a potential uncontrolled hazard of an explosive atmosphere near the vehicle likely to cause injury or death if ignited. 6) The practice of opening the hatch to dip the tank places the operators in potential danger - exposure to a potentially explosive vapour. 49 After setting out the background facts to the explosion, Dr Green reviewed the operation of the bitumen spray tanker by reference to three relevant aspects, namely, the cleaning of the spray bars, the dipping of the tank and the operation of the LPG gas system; the prevailing weather conditions, according to information received from the Bureau of Meteorology, were referred to in the report as part of his overall consideration. Also, Dr Green specified the requirements for an explosion to occur, in terms of the circumstances of the present case, as being fuel in the vapour phase at a concentration above the lower flammability limit and below the upper flammability limit, oxygen (usually as air) and a source of ignition when the temperature of the system is below the autoignition temperature of the fuel. After referring to the properties of the four fluids carried on the spray tanker here (bitumen, Mexcut B, kerosene and LPG propane gas), Dr Green reviewed the available sources of oxygen and potential ignition sources on the basis of comments made by the persons interviewed and the various written statements prepared - much of that material has been referred to earlier in these reasons in dealing with the prosecutor's evidence. 50 Based on the observations of Mr Anolek and Mr Harper, Dr Green was of the opinion that a significant vapour cloud, coming from either the vent pipe on the spray tanker or from the open hatch (or from both), ignited and where the injuries to Mr Newton were consistent with him walking on the top of the tanker and being struck by a fireball from below. The circumstances existing at the time as to potential ignition sources, found by Dr Green to be some six in number as earlier specified, were reviewed in detail in the report. Dr Green concluded - "It is clear that there are several ignition mechanisms that could have been present to cause this explosion, which on the information that I have received cannot be ruled out". 51 Of particular relevance, Dr Green examined the work practices followed and stated in his report as follows : The practice of discharging cutter fluid into the bitumen tank, while common in the industry, is not in accordance with AIP CP-20, "Code of Practice for Handling Bitumen" (section 5.3.7). This code of practice recommends the use of a second tank to hold cutter fluid which can be used to clean the pipes with a return to the secondary tank. An equivalent safe practice for the discharge of cutting fluid into the main bitumen tanker would be to have a vapour recovery line in the process with no direct vent to atmosphere in the main tank. The practice of having a dip stick under the top hatch exposes the operator to a flammable atmosphere. The personnel were not given breathing apparatus for this task and were not instructed in these potential hazards. Boral should have known about these hazards as they are clearly identified as part of a number of potential problems created in handling bitumen (AIP20). 52 In his oral examination-in-chief, Dr Green gave the following important evidence about the risk of an explosion occurring in the then existing circumstances if ignition occurred : Q. But whatever was the source of the ignition, the situation in relation to this particular tanker on that particular day, in the circumstances which you been told about was, in your opinion, such as would create a risk of explosion if ignition occurred? A. That is certainly true. Q. Now, in relation to that proposition, I ask you what matters, in your opinion, on that particular day in relation to that tanker, created a risk of explosion? I am not asking you what caused the explosion. I am asking about the risk of the explosion if ignition happened? A. In terms of an explosion occurring you need a number of factors to come together. They are a source of fuel, some oxygen or air mixed with the fuel and an ignition source. Now, in terms of the fuel in the tanker, or in the vicinity of the tanker, you have a number of sources that can give rise to an explosive vapour. They are the cutters that are used in the bitumen plus the LPG that is used to heat the bitumen tank. The practice of cleaning out the spray baths with cutter fluid and then pumping it into a heated tank will cause vaporisation of a part of that cutter fluid and create another vapour that, when mixed with air, becomes a flammable mixture and under those conditions you have a higher risk of an explosion occurring. Q. Of course, you have told the Court that the availability or introduction of the cleaning fluid, the cutter, into the hot tank created the risk of creation of flammable material. Is that what you are saying? A. Yes. Q. Did it make any difference whether or not the level of bitumen in the tank was high or low? A. It probably doesn't have too much effect, except that you tend to have a fairly large vapour space within the tank when the tank level was low, so that you get production of vapour from injection of the cool liquid into the hotter tank. You will get a positive pressure in the tank and this will try then to escape by any means possible. In terms of the tank design, it usually leaves through the vent pipe within the tank, but it can also leave through the hatch, if the hatch is opened. Q. In relation to that last, was there any risk, in your opinion, in opening the hatch at that time, that is, after the introduction of the cleaning solvent into the heated tanker? A. Because you tend to have a slight positive pressure within the tank, whenever you open the hatch you will tend to get vapour coming out and conversely, probably get air going into the tank. So you get this mixture of vapour with air that forms an explosive mixture. Q. But is that not a risk any time you open the hatch? A. To a certain extent it is, but it is more so just after you have injected cold fluid because you have actually got a positive pressure within the tank. Under normal circumstances there is an equilibrium between the vapour above the tank and the actual liquid in the tank and so, on opening the tank lid, in those circumstances you are not going to get so much of an interchange in terms of atmosphere. Q. Yes, but instead of a negative, I am asking you when the hatch is opened in the circumstances that cleaning fluid has just entered a heated tank, are you telling the Court there is a higher risk of an emission of flammable gases? A. Yes. Q. Again, will you tell the Court why that is so? A. Because you have got a system that is not totally in equilibrium. Because the cold cutter fluid is being heated by the bitumen liquid, you are getting vaporisation. This puts a positive pressure on the tank. With the hatch open that will flow out through the open hatch. Q. Well, you know, do you not, that the bitumen is normally or ordinarily combined in the tank with methylated spirits - sorry, kerosene? A. Yes. … Q. I put it to you that you know that the content of the tanker had not ordinarily at times of administration, had not only bitumen, but a bitumen mixture with a solvent called kerosene? A. Yes. Q. Now, at the time that the hatch is opened is there a risk of an explosion at that time? A. There is a risk. If you are doing certain types of work on the tanker, but you would not, without injection of cold fluid into the tank, expect to get sort of the positive pressure in the tank that will give you that interchange of, or the mixture of air and vapour, in quite the same way. Q. You are telling the Court, are you, that it is that particular time, after the introduction of the cleaning fluid, that there is a higher risk? A. Yes. 53 As to the reference in the Code of Practice at para 5.3.7 that cleaning solvents, such as the Mexcut B used here, should not be discharged into the bitumen tank but instead returned to a separate storage facility, Dr Green gave the following evidence as to the importance of that recommendation : Q. Now that particular part of the Code of Practice is contained within the subject matter of cleaning of pumps, isn't it and eternals? A. It is, yes. Q. And the recommendation, to put it in other language, is that there be a separate solvent storage facility for that task? A. That's correct. … Q. Is that requirement an important one in your opinion? A. I think so because one of the dangers of this type of operation is the injection of cutter fluid which is normally at ambient temperature into octanes and therefore you get vaporisation and usually the formation of a vapour cloud as a result which does increase the risk of explosion and by having a separate solvent storage facility which you pump back into rather than into the tank containing bitumen cutters, so you actually avoid that situation being formed. Q. Right. And is there any in your own opinion any time taken after the introduction of the solvent, the cold solvent, for the formation of a vapour cloud? A. You have probably got a time over a ten or fifteen minute period by which this occurs after injection so that would be a time of highest risk. Q. So, you say there is the highest risk, what, immediately after or a period of ten to fifteen minutes after? A. It's a gradual process that you get vapour and injection from the tank so it's a risk that will carry on from injection over a fifteen minute period. Q. What happens after the period of fifteen or twenty minutes? A. Basically there is no more emissions from the tank because the tank's settled back into an equilibrium state. Q. What you do you say at that time is the consequence so far as risk is concerned? A. The risk declines back again to what it was when it just contained cutters and bitumen. Q. So there is a change in the risk as time goes by after the introduction of the cold solvent into the hot tank? A. Yes. … Q. Assuming what is introduced is a quantity of four litres into a hot tank where the level of bitumen in the tank is low, do your calculations with that assumption take you to the conclusion that with the introduction of air there is a risk? A. Yes. Q. And again is the risk a risk of any significance? A. Yes, because you have this explosive vapour cloud that may be as much as twenty cubic metres being formed. Q. It does require an opening or exposure to air? A. If you look at the design of the tanks they do have a vent pipe on them so you don't have to open the hatch to get that vapour to actually mix with air, it can come out through the vapour pipe and he discharged below the tank underneath the tanker and sort of drift away from that point. Q. So, in the event that cold solvent is introduced into a hot tanker, does not the gaseous build-up which I have described and quantified, doesn't that escape through the vent rather than by interaction with the introduction of air when the hatch is open? A. If you open the hatch while you are still venting then you will vent through the open hatch as well so you will have a discharge from both points. 54 In order to avoid the dangerous consequence of a risk of explosion after the introduction of cold solvent into a hot bitumen tanker, Dr Green, recognising the operational need to measure the contents of a bitumen tank on a spray tanker, gave this evidence : Q. Would you tell the Court what those consequences are, if you understand the assumption that, contrary to what you say should occur, the cold solvent introduced into the hot bitumen tanker? A. If the solvent is discharged into the tanker prior to opening the hatch a system should be devised where you don't need to open a hatch and you can put a dip stick through roof like you would at a petrol station or in your own car. The reason for doing that is, by having a fairly small orifice, you actually limit the escape of vapours from it. Q. Your last answer was - what was that? It would be better not to have to open the hatch? A. That's right and have some small port by which you put the dip stick into the tank to limit the escape of vapours from the tank. Q. Have you seen that done? A. It's done on various tankers. Whether it's done on the bitumen tanker, I don't know but I gather this tanker was modified in that way after the accident. 55 Dr Green was cross-examined extensively by Mr Simpkins . Largely, the witness was challenged as to the opinion he had expressed, as summarised above, by reference to a number of propositions of a scientific nature concerning the effect of mixing cutter with bitumen in the tank and the resultant degree of vaporisation with a flammable condition. In that respect, there was considerable attention to the chemical make-up of the various liquids involved in this matter (bitumen, kerosene and Mexcut B) and the scientific laws applicable to their reaction under certain conditions. The questions were directed to the defendant's proposition that any vapour or gases in the tank at the time the hatch was opened by Mr Newton were below the lower flammability level. And, so it was suggested by the defendant, there was no relevant detriment to safety created in the circumstances as they developed. The following cross-examination of Dr Green makes the point : Q. Is it correct to take from that that the conclusion that you reached in this report was that within the tanker itself at about the time the explosion or fireball event occurred, there was available as a fuel vaporised kerosene and/or vaporised mexicut B? A. It is possible, yes. … Q. Again correct me if I am wrong, is it the theory you put forward that mexicut B vaporises technically the quantity of vapour that you calculate in this section which provided some positive pressure within the tank? A. The tank would have vaporised, yes. Q. Is the conclusion of the calculations you have endeavoured to perform there there should be a positive pressure within the tank? A. Yes. Q. The theory that you propounded being when the hatch was open with the positive pressure had the consequence that the fuel being either kerosene or mexicut B or a combination was propelled from the tank into the atmosphere? A. That is one possibility. The other possibility is that the pressure is actually relieved in part by the vent within the tank so it actually comes out underneath the tank as an ongoing process. Q. Just so I can understand the logic of theory you propounded, it is that the mexicut B by virtue of being heated was vaporised providing positive pressure within the tank? A. Yes. Q. That positive pressure had the effect of forcing out of the tank either through the open hatch or through the pipe or both, mexicut B and/or kerosene in vaporised form in the tank? A. Yes. It would also form an explosive mixture within the tank at the same time. Q. Does that notion proceed upon the footing that there was a mixing of oxygen with vapour within the tank prior to the hatch being opened? A. As you pump out the bitumen from the tank, the vapour space or the level in the tank drops and that is going to be replaced by air. So you have got air in the tank at the time when you are injecting the mexicut B. The vaporising part of that liquid would form an explosive mixture within the tank itself. … Q. It is the gas, correct me, the calculation of dilution affects the rates 142, the gases whatever they may have been within the tank, would have been reduced to below the flammability limit of either kerosene or mexicut B? A. That is correct. Q. If dilution within the tank occurred to a level of 142 times by the time the hatch was opened, the gas expelled from the hatch would be below its lower flammability level? A. It would certainly have a cloud of that size in the tank, because you are expelling stuff from the tank meaning you get in more air in so you find you are actually above the flammability level. That is based on the assumed requirement you have actually dilutant flowing below flammability limit. In practice you have not got quite as high a quantity as that. It is more or less the size of the cloud form. Q. The one thing you have not calculated is the extent to which there had been dilution within the tank? A. No I have not calculated that specifically. Q. All you have calculated is the dilution which would be in order for the gases, whatever they may have been, to be placed below the lower flammability limits? A. Yes. 56 In re-examination, however, Dr Green gave this evidence as to the flammability level of the vapour : Q. Lastly, having heard those questions which were put to you by Mr Simpkins on the likely volume and weight of the gaseous emission from the tank, is there anything in regard to your observations on that aspect that you would like to now change? A. Only the volumes of gas likely to be given off is less. The volume of gas or vapour is likely to be less than what is contained within the report and that makes it more likely you have a flammable atmosphere within the tanker itself. It leads to the conclusion ignition occurred probably from within the tank. That is the most likely position for it. Q. Is there anything in your report, the report which you have prepared for the WorkCover Authority you would seek to change as a result of that observation, or do you say your report admitted that? A. It covers that. There are a couple of ignition sources. It talks about pyrophoric deposits within the tanker and also cutter which could have formed around the heating pipes. Expert evidence for the defendant 57 Mr Simpkins called evidence for the defendant from Brian Frederick Gray, Professor of Chemistry at Macquarie University and also Honorary Professor of Mathematics at the University of Queensland and Honorary Research Associate in Mathematics at the University of Sydney. Professor Gray, like Dr Green, was eminently qualified in this field and held the degrees from the University of Manchester of B Sc (Hons 1), M Sc, Ph D and D Sc. He was a Fellow of the Royal Australian Chemical Institute, Institute of Mathematics and its Applications and of the Australian Mathematical Society; he had membership of the International Association of Arson Investigators and the Combustion Institute (Australian New Zealand Section). Professor Gray claimed special competence in the areas of self-heating, spontaneous combustion and spontaneous ignition of many materials occurring in industry and agriculture as very common causes of fire. In particular, the areas of expertise in which he had had experience covered fire causation, vapour ignitions, spontaneous ignition of wood stains, paints and oils on rags, spray can propellant incidents, arson detection, fires resulting from hot or warm industrial products and fires resulting from stacking large amounts of industrial products. Again like Dr Green, Professor Gray had published widely and had had consulting experience in relation to the review of fires and the causes thereof in many industries and situations. 58 However, and unlike Dr Green, Professor Gray conceded he had "not been involved in a case involving a bitumen tanker before" and he agreed that, apart from the present case, he had not "seen any material analysing accidents, incidents, fireballs or explosions of bitumen tankers". Although Professor Gray agreed in cross-examination with the proposition that "certain hazards ... certain risks attached to the use and operation of bitumen tankers", he put those risks "particularly at the depot when the tanker is being filled" and said that "presumably" bitumen tankers do involve risk - those comments seemed to be based on Professor Gray reading the Code of Practice and he accepted, by reference to Dr Green's curriculum vitae , "that there are fires in bitumen tankers, fireballs or explosions on bitumen tankers which were and remain unexplained". In present respects, Professor Gray said he had not been asked to advance an explanation for what occurred here and, in any event, he had "not been given any evidence on which an explanation could be based". 59 Professor Gray was shown during his cross-examination an article entitled "Case Histories of Incidents in Heated Bitumen Storage Tanks" by F M Davie et al (J Loss Prev Process Ind, 1994, Vol 7, No 3 at p 217) of the Department of Chemical Engineering, South Bank University, London, UK, which article was later admitted into evidence as part of Mr Brezniak's case. Notwithstanding Professor Gray's lack of knowledge about such cases, the abstract from the said article stated : A study has been made of 73 case histories of incidents involving heated bitumen storage tanks. The majority of incidents were found to be due to operations such as charging and discharging of tanks, including overfilling which can lead to lagging fires and exposure of heater tubes. A number of incidents were the result of spontaneous ignition or unknown causes; it is proposed that regular cleaning of tanks would reduce the number of these incidents. 60 By way of illustration only at this stage, the article referred (at p 220) to incidents due to spontaneous combustion and unknown origin in that "It has been found that bitumen deposits can undergo a smouldering reaction dependent on the availability of oxygen" and that has occurred "when manhole covers have been left open or raised by strong winds … These situations lead to an increase in the oxygen concentration around the deposit and may be due to an increase in the reaction rate of the smouldering deposit or the presence of pyrophoric material. Deposits left to accumulate can smoulder, and, in situations where cross-ventilation occurs, such as a manhole cover being left open, can reach high temperatures increasing the risk of fire". Further, the article noted (at p 221) that "It is known that deposits on the underside of the roof of heated bitumen storage tanks can smoulder, and, if sufficient oxygen is present, can reach high enough temperatures to act as an ignition source to flammable vapours". I will return to this article in dealing with later evidence given by Dr Green. 61 A report dated 23 February 1998 was prepared by Professor Gray at the request of the defendant and, as the opening words thereto stated, he offered "critical comments from the forensic standpoint on the documents forwarded in the order listed, ie each of the Summons issued by the WorkCover Authority, the Affidavits in support of the Summons, WorkCover brief including witness statements and the report by Dr A R Green". Principally, however, his report attended to answering the approach and opinion expressed by Dr Green in his report. Also, Professor Gray's evidence attended very much to a pure scientific basis for concluding that there was simply no explanation for the fireball, and certainly not one for which the defendant could be held responsible. Nevertheless, it seems to me, it is apt to emphasise that a fireball indeed occurred on top of the bitumen tanker when Mr Newton was performing his duties and as to which there was considerable evidence, both oral and documentary, as to the risk involved in handling bitumen and cutback bitumen. 62 Professor Gray agreed with Dr Green that the fireball resulted from ignition of a substantial release of flammable vapour, less than 50 cubic metres. Specifically as to the remaining conclusions made by Dr Green, as outlined above, in para 1.2 - Summary of his report, being conclusions (2) to (6) thereof, Professor Gray disagreed with them as being either "not possible" or "possible but improbable" or "very unlikely" or "quite wrong" or "largely wrong". To the extent there was ignition, Professor Gray was of the view that the source of flammable vapour which ignited was LPG (propane) from a gas bottle, used to feed gas burners to heat the bitumen, located on each side of the rear of the truck. It should be noted that Dr Green also considered whether a leak in the LPG pipework or valves at one of the burners or cylinder could be a possible source of fuel for the explosion but discarded that on being informed by Mr Hannan that there was no fault in the LPG system following his inspection and discussions with Mr Skidmore. Also, the Critical Incident Report prepared by Mr Skidmore did not mention any fault with the LPG system as a possible source of the fuel which ignited to form the fireball. 63 In his oral examination-in-chief, Professor Gray referred to a basic proposition of Dr Green that the Mexcut B cutter injected into the tank during the blowing of the bars created a flammable vapour able to escape through the hatch when it was opened by Mr Newton. He used ideal scientific laws to conclude that the introduction of from 5 to 8 litres of Mexcut B would produce vapour being "a very small fraction … less than 1%" of the gas or vapour otherwise within the tanker. In concluding there was no relevant flammable vapour created as a source of fuel which could have been ignited to create the fireball here, Professor Gray gave the following evidence : Q. What does that calculation tell you about what might have happened in the storage tank of the bitupaver as a result of the introduction of Mexcut B assuming that 5 to 8 litres was introduced and it vaporised at the rate of 10 per cent? A. Well that tells you if you go along with Dr Green's assumptions about the volume of liquid and what fraction of it would be vaporised and do the calculation according to this method which gives you the correct answer then you finish up with a volume which is 10 times smaller than Dr Green's assumption and that would be the volume of vapour that would be expelled from the tanker if that indeed did occur. … Q. So whilst you have done this calculation do I understand this correctly, it's not your opinion that the quantity of gas that you have calculated was given off by the introduction of the cutter to the tank? A. It's a correct calculation of Dr Green's scenario. Q. But do you hold the opinion that it is a calculation of which has any scientific validity for the purpose of analysing what happened in the tanker? A. No. … Q. If one assumes that the two liquids are immiscible and that this quantity of Mexcut B vapour was given off in the tanker what would otherwise happen with the gasses or vapours within the tank at the time that that occurred? A. Well, what would be the most likely scenario which would have to happen would be that the gas at the top of the tank would be pushed out of the vent pipe. The vent pipe, this is into the top of the tank, so if vaporisation of Mexcut B occurred on the liquid surface that would act in a sense like a piston which would push the gas in the whole tank upwards and the first approximation would be to say that last in would be first out. The vapour which is immediately vaporised if this Mexcut B scenario is correct - which I don't agree with - nevertheless given whatever volume of Mexcut B is vaporised above the liquid that would push out vapour which is nearest to the vent pipe which is at the top of the tank. That would not be Mexcut B that would be whatever was in the tank at the time. … Q. If one assumes that by the time the hatch on the tanker was open that there was no positive pressure but the state of equilibrium, what would happen to the vapours in the tank on the opening of the hatch? A. Very little I would have thought. There would be slight mixing of air with the vapour at the top, where the vapour at the top is. The difference would not be all that great. So there wouldn't be a high convective effect from the top of the tank because the density of the vapour, or depending on what it is, but certainly the density of the vapour, or Mexcut B vapour is much greater than that of air, so even though it was hotter than the air there would be a cancellation of effect of density, of density effect. Hot air rises in cold air because the molecular mass of air is fixed but hot heavier hydrocarbon will not necessarily rise in cold air because the density of hydrocarbon vapour is significantly greater than that of air in the first place. So you would have to raise the temperature more than enough to compensate for the extra density in the first place. So it's very difficult to say without knowing precisely what the composition of the vapour on the top layer of the tank was what would actually happen when you open the hatch. But I think it's not a sound proposition that a positive pressure would be there after the period of time that had elapsed which is said to have elapsed between the blowing of the bars and the opening of the hatch which I understand to be of the order of 15 minutes; ten or 15 minutes. 64 Notwithstanding that Professor Gray expressed his opinion as to the creation of a flammable vapour cloud by reference to the bitumen in the tank, the injection of a small quantity of Mexcut B and the miscibility of those two substances, having in mind their chemical characteristics to perform in a particular way contrary to that suggested by Dr Green in light of the physical structure of the tanker, Professor Gray, I think, displayed a somewhat incomplete knowledge of the fundamentals of the substances involved. For instance, much of Dr Green's analysis of what likely occurred relied upon the chemical nature of the substances present (including by reference to various articles in learned journals, such as the Case Histories of Incidents in Heated Bitumen Storage Tanks earlier referred to and another article by F M Davie et al (J Loss Prev Process Ind, 1993, Vol 6, No 4 at p 203) entitled "Mathematical Model for the Self-heating of Deposits found in Heated Bitumen Storage Tanks"), but Professor Gray conceded he had never found out the composition of bitumen or, as utilised by Dr Green, the molecular weight of bitumen because, as he said, "It is not a relevantly defined quantity … not relevant as far as ignition is concerned". Indeed, Professor Gray went further in cross-examination and challenged a number of Dr Green's propositions by asserting that asphalt did not mean bitumen and that bitumen did not contain a percentage of asphaltenes. However, the Encyclopedia of Chemical Technology (Kirk-Othmer 3rd ed, Vol 3 at p 284), admitted into evidence, in defining the word "asphalt" stated that its "predominating constituents are bitumens that occur in nature or are obtained in petroleum processing. Asphalts characteristically contain very high molecular weight hydrocarbons called asphaltenes … Bitumen is a generic term … composed principally of high molecular weight hydrocarbons, of which asphalts, tars, pitches, and asphaltites are typical. Canadian and European practice … and geologists and archeologists in the United States use bitumen or asphaltic bitumen as a synonym for asphalt, and apply asphalt to the mixture of bitumen and inorganic matter". 65 In relation to the source of fuel (para 3.1 of his report) and the source of oxygen (para 3.2 of his report) enabling the formation of a sufficient flammable vapour cloud to create the fireball, Dr Green, after considering the chemical composition of the substances and how they reacted, concluded that the opening of the hatch on the top of the tanker by Mr Newton provided the means by which air could enter the tank and vapour leave the tank but "Due to the buoyancy of the vapour inside the tank and the recently injected cutter fluid into the tank, vapour would escape and engulf Mr Newton". As to the ignition source (para 3.3 of his report), Dr Green emphasised in particular the pyrophoric deposits on the tanker lining, pyrophoric material from the tank bottom and bitumen soaked fibre insulation around the hatch on being exposed to a sudden atmosphere of oxygen in the air when the hatch was opened. Professor Gray concluded in those respects, after disagreeing with Dr Green's calculations relating to the chemical properties and reactions of the substances involved, that Dr Green's conclusions "are so full of logical and physiochemical errors that they are totally misleading quite apart from the questionable assumptions made as to amounts of material and non-mixing of what in fact are highly mutually miscible (soluble) liquids … It would not be flammable due to its composition even whilst above ambient temperature … It could not have been an explosion or ignition hazard. Similarly, denser cool air entering the hatch (if indeed it did so) would be irrelevant as far as ignition hazard is concerned as it would simply be diluting and cooling a mixture already too weak to ignite regardless of its temperature". In the circumstances, Professor Gray considered the pyrophoric deposits were not a possible source of ignition because as "the mixture is always below its lower flammability limit we can rule out this mechanism of ignition of the gas inside the tanker. In fact what we have shown in terms of mixture strength rules out any mechanism since the vapor inside the tank is not flammable". However, and consistent with Dr Green's approach, the learned authors in the article on the Mathematical Model for the Self-heating of Deposits found in Heated Bitumen Storage Tanks concluded (at p 208) : The majority of tank fires which are thought to be caused by self-heating of deposits on the underside of storage tank roofs occur when air is allowed to pass across the surface of the deposits … In a situation where the oxygen concentration has been reduced, deposits may be allowed to build-up to a level where they would be considered active under normal atmospheric conditions. Subsequent ingress of air during charging or discharging of the tanks or prior to cleaning of inert tanks would expose the deposits to an increased oxygen atmosphere and could "activate" previously dormant deposits, as the process is oxygen diffusion-controlled on the deposit surface. 66 The self-heating of pyrophoric deposits in a bitumen tanker caused by an increased oxygen atmosphere leading to tank fires, as concluded in the above mathematical model, and referred to by Dr Green here as "the chimney effect", was resisted by Professor Gray who gave the following evidence : Q. So when the hatch cover is open it would cause, I put it to you, the air to be sucked through the vent pipe, discharged into the hatch space of the tanker, as you yourself said would happen, and sweep its way towards the manhole chimney which I took you to a moment ago. You don't agree with that, do you? A. It's a possibility but I think - I wouldn't like to say that would be a likelihood. It's a very tall - it's drawing a very long bow to say that those two devices could act together as a chimney. Q. I want to suggest to you, respectfully, that if you were not giving evidence in this case for the defendant you would readily agree that the chimney effect would occur immediately upon the opening of the hatch of the tanker? A. No I wouldn't. Q. In circumstances where there is a vapour pressure inside the tanker before the hatch lid is open? A. I'm sorry. Is there a question? Q. That is a question. A. No, I wouldn't agree with that. Q. When you say it is drawing a long bow, I want to put to you that it is drawing the description of the most likely occurrence? A. In the complete absence of any physical evidence I would hate to speculate what was the most likely occurrence because there is no physical evidence as to what actually burned or what the source of ignition is so it is all pure speculation. Q. I put it to you it is a simple application of the chimney effect? A. There is no evidence that that occurred in these particular circumstances involving the two devices, a vent pipe and the hatch. 67 Professor Gray was pressed under cross-examination on the relevant effect of this aspect on the occurrence of the fireball and the following evidence emerged : Q. And if the chimney effect as described to you does take effect, does happen - if it does happen - I know you say it is a long bow - if it does happen, right? A. Yeah. Q. Then the flammable vapours would be discharged into a non-insulated space around the manhole, isn't that right? A. Is this with the hatch closed. Q. With the hatch open? A. With the hatch open the flammable vapours - are you asking me to agree that the flammable vapours would somehow be pushed from the tanker - we are talking about air that comes up through the vent pipe as the chimney effect? Q. Yes. A. Because that is air that comes up? Q. Yes. Would push the vapours in that area into the uninsulated - into the uninsulated space around the manhole? A. Well, I think that's wild speculation at best. Q. If there was any condensation of kerosene inside the manhole and the basket that was there that might turn into a vapour stream, mightn't it? A. The very fact that you have got air coming up through the vent pipe, if you want air to come up through the vent pipe and move into the region of the hatch you won't have condensation because you will have a much weaker mixture there by virtue of the hot air that has come up through the chimney effect. That's hot air. You can't have that coming in and having condensed kerosene vapour in the same region because if you have hot air coming up through a chimney effect it will weaken the mixture. … Q. Mr Anolek said at page 19 of the transcript lines 55 to 58 and page 20, the first eight lines, said that he could see and smell the vapours when he opened the hatch and I think you were here when he said that? A. I probably was here when he said that. Q. That is what he said. He said you could see and smell the vapours when he opened the hatch? A. That's not surprising on a bitumen tanker. The nose is much more sensitive to any of the GCMSs we have seen results from today. Q. What about Mr Newton's evidence that the top of the truck - the fumes were everywhere. He said that at page 44 line 38. Fumes were everywhere, he said. Do you say you would not be surprised by that at all? A. I beg your pardon. Q. Do you say you were not surprised by that account? A. I am neither surprised nor not surprised. It's a matter of fact if Mr Newton has remembered it correctly. Q. If the fumes were everywhere, something caused it, didn't it? A. Of course. Q. And if something caused it then you are here to assist us with that particular analysis, aren't you? A. Yes, yes of course. Q. Do you remember Mr Anolek's evidence at pages 19 and 20? He said that the vapours were particularly strong if you were circulating or getting your pump turning with the air coming out of the bottom of the truck? A. Yes. Q. Not only did you have those observations of those particular gentlemen who gave evidence which you heard, you have the Code of Practice for the Safe Handling of Bitumen Products, which is exhibit 18. It says, doesn't it, at 7.3.6 - can I read it to you, professor? A. Yes. Q. "Access by personnel to hot bitumen tank tops should be strictly regulated at all times. It should be avoided as far as is reasonably practicably during product movements into or out of the tank concerned. It should be prohibited during the blending of cut-back, during the raising of the tank temperature, during any outbreak of fire in the vicinity, during periods of high wind or during electric storms." Do you agree with those particular - - A. They seem sensible and reasonable. 68 In my view, the assessment of Professor Gray's evidence may be made in light of the approach he took to his task. During cross-examination as to the vapour which was said to have risen through the open hatch or leaked through the damaged hatch when it was closed, Professor Gray was referred to the observations made by Mr Anolek, Mr Newton and Mr Harper just prior to and at the time of the fireball; he remarked that the scenario put for the prosecution was an "interesting theory" and added that it was "an unknown event" and people "would be very happy to know … what has caused this but that is not going to happen because nobody kept any physical evidence unfortunately". The following evidence given by Professor Gray in this respect is instructive : Q. Why isn't it the case? A. There are plenty of other explanations, none of which has any support by physical evidence. Maybe you misunderstood me. By physical evidence I was referring to scientific evidence, forensic evidence not the evidence of witnesses; and there is a complete - unfortunately a complete absence of any scientific evidence as to what the flame was composed of and so on. Or whether there was any flame inside the tank et cetera et cetera. Q. It would have been trivial, as you pointed out why you hadn't done it yesterday, why didn't you take some samples of the vapours inside the tank? A. The question is why I didn't take it? But as a theory, anybody has a theory or a scenario. The way scientific methods work, is you have a scenario, you are going to investigate a fire. You take samples to see whether there was, to find whether there is any evidence of combustion event inside the tank. As you yourself demonstrated yesterday with the GCMS operation from the laboratory which was set at maximum sensitivity, it is possible to detect extremely small amounts of hydrocarbons or whatever, we could all have been discussing solid evidence if these kinds of measurements had been taken. Newton's overalls, for example, could have revealed what was the composition of the flame or the hot gas that engulfed and burnt him; if samples had been taken. There is the kind of physical samples that I'm referring to, not the statements of witnesses. Not that I'm down-playing the statements of the witnesses but it seems to me that anything that isn't based on measurements of that kind is scientific speculation unfortunately. It's possibilities and not probabilities. Q. Isn't really that it. And I intend not to be disrespectful, that your task in analysing those circumstances which led to the incident, the accident -? A. I'm sorry, that isn't my task. Q. No, if you permit me to conclude the question. Your task is simply to raise as many doubts about the authenticity of likelihoods as possible. To say it's possible but it's pure speculation. To say it may be but it can't be proved. Isn't that what your task is? A. Well, not really, but I don't see any other possibilities because there is no scientific evidence presented as to what actually burnt, what may have been the source of ignition? I mean we can all sit here until the cows come home and construct theories as to what might have happened. Something may have come out of the hatch and we can argue about whether they are scientifically credible or plausible or flawed or whatever but. At the end of the day with no physical evidence to say it was LPG burnt Newton's overalls. It was kerosene or it was Mexcut B or a mixture of bitumen or Mexcut B, or whatever, there is no evidence to say which of those it was. And there are four flammables on this truck. Perhaps it was a diesel. There would be diesel in the four. Whether it was diesel or petrol in the four to run the truck, there's kerosene and Mexcut B and also LPG, and there is no physical chemical evidence as to which of those got into Newton's overalls and burnt them. Or whether there are any combustion products inside the tanker. Q. Did you ask whether you could have access to the tanker? A. Three year later there is no possibility of getting any measurements. Prosecutor's expert evidence in-reply 69 In a further report dated 24 September 1998, Dr Green summarised his findings in light of the evidence given in the case and the report of Professor Gray, including by reference to various scholarly journals. Dr Green summarised his opinion that "Newton was burnt because he was required to open the hatch in order to dip the bitumen tank. The opening of hatch allowed a fuel/air mixture to flow out of the hatch forming a flammable vapour/aerosol cloud on top of the tank which was subsequently ignited to form a fireball. The addition of Mexcut B provided additional vapour and mist to the vapour already in the tank. The injection also added a slug of air to provide upward movement of vapours in the tank". 70 Dr Green's further report, which was comprehensive and very detailed, reviewed the occurrence of the fireball as an event requiring an ignition source within a flammable cloud of fuel. He conducted such review by reference to the emission of flammable material from the tanker (including eyewitness accounts of vapour/fuel outside the tank, the formation of a hot vapour trail and the chimney effect), the conditions inside the bitumen tank (particularly as to kerosene composition, bitumen molecular weight, calculation of the equilibrium vapour fraction in the tank, dilution in the tank, time dependent processes, effect of addition of Mexcut B, local factors and the formation of a vapour trail), ignition (as to sources, flame traps, pyrophoric ignition and self-heating and possible sources of ignition), the Code of Practice and irregularities with the information gathering and distribution process. In that last-mentioned respect, Dr Green emphasised the modifications made to the tanker by the defendant in fitting a new hatch lid before Mr Hannan was able to visit the site and inspect the tanker. 71 In the result, Dr Green expressed in the further report the following opinion : The main contributing factor to this accident was the need to open the hatch to dip the tank. This action exposed Newton to the fumes inside the tank which were wafted up by the chimney effect on an open hatch. The accident could have been avoided if the dipstick is repositioned outside the hatch area thereby removing the need to open the hatch. A second contributing factor was the suck back of Mexcut B into the tank. This provided additional vapour and air into the tank. This would have stirred the vapour space of the tank and would have forced vapour and air through the vent pipe to the underside of the tank. It would be preferable if the cutter was pumped back into its holding tank. Spillage into the thermal fibrous lining substantially increases the risk of spontaneous ignition. Since the tank is fitted with a pump and bitumen is normally transferred while on the road using the pump. The practice can also be employed at the depot. General comment on the proceedings 72 The evidence in this case was both detailed and extensive. Apart from the eyewitnesses, there was the expert scientific evidence of Dr Green and Professor Gray which travelled through pure scientific theory as applied to the circumstances of the subject incident but as to which the opinions expressed were in direct conflict. Counsel provided final submissions in written form and supplemented them orally at the hearing. I wish to express my gratitude to counsel for their helpful assistance in this case in my endeavour to resolve what I found to be quite complex issues of fact as to how the fireball may have occurred. However, the evidence of the lay witnesses as to what they actually saw immediately before the fireball and of the fireball itself when applied to what was said by the expert witnesses enabled me to better assess and put in perspective that expert evidence and the opinions expressed. Submissions - the prosecutor 73 As to the charge in the first matter alleging a failure to provide a safe system of work, Mr Brezniak identified from the evidence the defects which he submitted were established : (a) The hatch cover should not be open or opened after the introduction of the cutter fluid into the tank. (b) The dipping procedure should not require the opening of the hatch. (c) The dipping procedure involved contact with carbonaceous material and pyrophores which can, in contact with the diluting vapour, cause ignition. (d) The hatch lagging and the cotton waste used for dipping were impregnated with fuel and alight after the fireball. These impregnated materials are a source of ignition and some alternative less absorbent material might be used to minimise the risk of ignition. (e) The practice of top-filling the tanker at the depot is a practice which can result in the impregnation of the insulation around the hatch. This practice is not a necessary practice in the circumstances since there was a pipe and pump on the tanker for bottom filling. The risk of ignition can be substantially reduced by bottom filling of the tanker. (f) It is preferable for the cutter fluid to be pumped back into holding tank rather than permit it to be sucked back into the tanker after the bars have been cleaned. Each of the foregoing are matters integral to any safe system of work and the presence of pyrophores in the tanker to the proper maintenance of plant giving rise to an environment free of risk to employees of the Defendant. 74 As to the second charge concerning the alleged failure to provide such information, instruction, training and supervision of employees necessary to ensure their health and safety at work in respect of measuring the contents of the bitumen tank, Mr Brezniak made five main points : first, Mr Newton ascended the tank upon the instructions of Mr Anolek at a time when the cutter fluid was diffusing through the tank and that was dangerous; second, the circumstance that at the time Mr Newton dipped the tank it was only slightly filled and that there would have been exposure of the pyrophoric material was not something within the knowledge of either Mr Newton or Mr Anolek; third, Mr Newton had been given a safety handbook but absent any guideline or information as to the steps to take when measuring the contents of the tank with the dipstick; fourth, although employees were required by the defendant to give written acknowledgement of having read the rules and instructions there was not any expansion of what was required by way of any particular safety lessons, precautions or directions; and, fifth, there was no acceptable record produced by the defendant as to the actual information, instruction, training and supervision of its employees. 75 In a real sense, the following oral submissions made by Mr Brezniak encapsulated the prosecutor's case : The cutter had just been injected into the tank. The tanker was only minimally filled. There was a very small amount of bituminous material in it and the dangers which the code of practice at item 3.3 point to … are we say clearly heightened by reason of the low level of the bitumen tank and it is clear and the recommendation at 7.3.6 is that access by personnel to hot bitumen tank tops be strictly regulated at all times. It should be avoided as far as is reasonably practical during product movements into or out of the tank concerned. It should be prohibited during the blending of cut back. This was a case where the man Newton ascended the tank on the instructions of Mr Anolek, the driver of the tanker during and after the injection of the cut back. It was at a time when there was the blending of the cut back, the Mexcut B and we say the system of work was quite obviously dangerous given the resultant access to the atmosphere occasioned by the opening of the hatch on top of the tank so it appears as well that the employer really was not aware of the risk despite the code of practice. It permitted that to take place. There seems to be no knowledge of the heightened risk by reason of the small quantity of bituminous product in the tank. … It is simply the point … that the occurrence of an accident and the sustaining of injuries by an employee will certainly represent a relevant offence and the existence of a risk to the health and safety of employees and the seriousness of that risk, however it is not the accident itself which constitutes the offence but rather the failure of the employer to ensure that its employees are not exposed to risks at work. We say in our submission this is a case where when you look at what did happen, when you hear what Anolek and Harper and Newton said about what happened on the day that this was an accident waiting to happen. The risks were there. 76 As to the scientific evidence, Mr Brezniak submitted that the first report of Dr Green was a description in a scientific way of the phenomenon which took place or a description of likely causes of the incident; Dr Green's second report attended to the validity of the methodology earlier followed by him and provided a detailed answer to the criticisms made by Professor Gray. On the other hand, Mr Brezniak put that Professor Gray's evidence did not propose a scenario or hypothesis for the incident which occurred but rather sought to demolish the argument put by Dr Green by reference to scientific theory but by ignoring the eyewitness accounts of what they had seen. Further, it was submitted that Professor Gray had sought to apply ideal scientific laws to a complex mixture without understanding the nature of bitumen or what it was. Therefore, so counsel submitted, the analysis by Dr Green of the events leading to and the causes of the explosion, or fireball, was undiminished by the theoretical criticisms of it made by Professor Gray. The offences had been established. Submissions - the defendant 77 Having in mind the way in which the particulars were framed by the prosecutor, Mr Simpkins submitted that there was an incident which occurred on 17 November 1994 when a gas ignited in close proximity to the defendant's bitumen tanker. The questions which then arose in relation to that incident were - did the gas which was ignited come from the tank? If so, was the system of work one which was unsafe by permitting the hatch to be opened shortly after the introduction of the cutter (Mexcut B)? In resolving the issues so described, counsel submitted that the prosecutor had to satisfy the criminal onus of beyond any reasonable doubt as appropriate to a case based upon circumstantial evidence; in other words, the prosecutor must exclude any reasonable hypothesis consistent with innocence and prove all intermediate facts necessary for such a conclusion beyond reasonable doubt. 78 Mr Simpkins referred to the uncontroverted evidence that there were other gases either in or capable of being in proximity to the tanker, namely LPG, so that the prosecutor had to prove to the appropriate standard there was Mexcut B vapour of sufficient quantity outside the tanker within its flammable limits to account for the event but with no LPG of sufficient quantity outside the tanker within its flammable limits to account for the event. Neither of those facts, so it was submitted, had been established. Mr Simpkins laid much stress on the point, as he said, "that an alternative explanation for the incident is what was ignited was not gas from the tank but was the LPG and, if that alternative explanation has not been negatived, then on this prosecution the Authority has not persuaded your Honour to the standard of criminal proof which is appropriate in a circumstantial case". That, in Mr Simpkins ' submission, was the short and complete answer to the whole case being found in favour of the defendant. He conceded that the Court "would, nevertheless, be entitled to say that the offence is not the explosion, maybe the LPG explains the explosion, that possibility can't be excluded. The offence is having a dangerous system of work. … it's sufficient in the circumstance if the vapour which was in the tank was shown to be flammable and capable of escape regardless of whether it caused this particular incident. I would have to accept that the short answer is an answer to the explosion, not necessarily a complete answer to the existence of dangerous vapours in the tank. I would need to persuade your Honour on the scientific evidence that the onus has not been discharged in that regard". In other words, in that situation one would then have to attend to the longer answer, that is, the scientific evidence. 79 Helpfully, if I may say so, Mr Simpkins summarised the defendant's approach in this way : I say two things. The Authority is experienced in formulating its charges. No doubt it takes advice as to what should happen and it can press what charges it chooses. If it formulates a charge that does not fit the circumstances, there is no reason why the ordinary consequence should not follow. Secondly, the fact that the unfortunate accident occurred does not necessarily mean that it occurred as a result of any unsafe system or any lack of training. Unfortunately, there are work accidents from time to time which involve no element of fault, no element of offence on the part of any employer. So the fact that the accident occurred, unfortunately as it may be, does not necessarily mean there was some available charge which, if formulated properly, could have been successful. That is the short answer. I move to the longer answer which has occupied several days of transcript. there has been a very wide ranging scientific debate. The difficulty that confronts your Honour is trying to work out what are the parts that truly matter. Does your Honour need to work out what is right on these points or work out what is right on some points and, if only on some points, what are the important ones. We have endeavoured in the written submissions to really advance for your Honour's consideration what we say are the important points. We hope to provide some assistance on what things might truly matter and what we wish to say about them. 80 Mr Simpkins attended in detail to the scientific evidence given by both Professor Gray and Dr Green and, in urging preference of Professor Gray's opinion to that of Dr Green, counsel's submissions were summarised generally as follows : 18. In determining whether the Authority's case has been made out (this would involve accepting that each of the intermediate factual matters referred to in paragraphs 6 or 12 had been established beyond a reasonable doubt), at least five matters need generally to be borne in mind:- (a) Dr Green's evidence is essentially scientific speculation on matters permitting of rational debate; (b) Dr Green's opinion is, at its absolute highest, merely one of probable cause; (c) Dr Green's opinion is contradicted in several important respects by Professor Gray whose scientific opinions are credible (and to be preferred, if it be necessary to go that far); (d) Dr Green's theory is inconsistent with a long time of uneventful pursuit of the practices complained of; (e) Dr Green's opinion fails to exclude LPG as an alternative hypothesis. 19. The proposition referred to in paragraph 18(a) is obvious, and Dr Green conceded as much from time to time. 20. The proposition referred to in paragraph 18(b) was conceded. 21. The Authority's submissions amply demonstrate the ongoing debate and the validity of the proposition referred to in paragraph 18(c). 22. If Dr Green's new analysis is correct opening the hatch of a bitumen tanker (whether in close proximity to "blowing the bars" or not) would permit a flammable vapour to escape - tankers hatches could never be opened with safety. This flies in the face of decades of experience … The validity of the proposition referred to in paragraph 18(d) is demonstrated. 23. The proposition referred to in paragraph 18(d) was conceded; the explanation being something that Mr Hannan said … For this reason alone, if for no other, the Authority has not discharged its onus of proof. 24. Unless there was a risk that otherwise existed as a result of what lay within the tank, the Code is irrelevant. In any event, upon its proper construction it has nothing relevant to say. Submissions - section 53 defence 81 Reliance was placed by Mr Simpkins on both limbs contained in s 53 of the Occupational Health and Safety Act as complete defences to the charges, namely - it was not reasonably practicable in the circumstances for the defendant to comply with the obligation created by s 15 (para (a)); and the commission of the offences, which was denied, was due to causes over which the defendant had no control and against the happening of which it was impracticable for it to make provision (para (b)). 82 At the core of Mr Simpkins' submission was the proposition that "If there was any risk … the existence and nature of it was something only able to be known upon reviewing matters of scientific debate and coming to a particular view about them. That made it impracticable to identify and attend to any risk." In that respect, counsel referred to McVernon v Royce Roofing Industries Pty Ltd [1988] 25 IR 383 at 385 and Cullen v State Rail Authority (NSW) [1989] 31 IR 207 at 218. 83 Mr Brezniak countered that adherence by the defendant to a safe system of work and to those requirements set out in the Code of Practice for Safe Handling of Bitumen Products would have prevented Mr Newton from ascending the bitumen tanker at the time he did. Indeed, counsel submitted, the modifications made to the tanker after the incident should have been made before; the availability of those modifications was evidence that the defendant had an insight of the circumstances which gave rise to the incident. The s 53 defence, therefore, should fail. Whether one or two offences 84 In opening the prosecutor's case, Mr Brezniak referred to the nature of the two charges and said that they related to "a somewhat different but factually identical set of circumstances of proof". From that, as earlier stated, Mr Simpkins relied on Boral Gas v Magill (37 NSWLR 150; 58 IR 363) for the proposition that the prosecutor was only entitled to succeed, if at all, upon one of the summonses because the same acts and omissions were relied upon for each charge. It is true, in general terms, that Boral Gas v Magill stands for that proposition. However, in the circumstances of this case, as it was in Boral Gas v Magill, I am of the view that the nature and content of each alleged failure is separate and distinct so as to constitute two contraventions of s 15(1) if otherwise made out. 85 Boral Gas v Magill was decided by a Full Court ( Fisher CJ, Hill and Hungerford JJ) of the former Industrial Court and, in dissent, Fisher CJ said (at p 153; p 364) "that s 15(1) states the offence. Section 15(2) provides further but not necessarily exhaustive particularisation". On the other hand, the majority ( Hill and Hungerford JJ) held, as the headnote in the report accurately stated (at p 151) - "While s 15(1) of the Occupational Health and Safety Act 1983 creates one general duty, each act or omission constituting a failure of a duty specified in s 15(2) or otherwise breaching s 15(1) is a separate offence under the section". Putting aside questions of duplicity which do not presently arise as separate summonses were issued, Hill J, in the majority, observed (at p 179; p 389) that "If, of course, the same act or omission falls coincidentally within more than one of the categories of failure set out in s 15(2) (or more than one of the sub-categories set out in each category), then, in my opinion, only one offence will be involved". But, in finding that not to be the case there where the alleged contraventions comprehended a failure to provide a safe system of work and a failure to provide appropriate information, instruction, training and supervision, his Honour considered there were separate and distinct failures and, therefore, separate offences. He explained it in this way (at p 179; p 389) : The gist of the offence created by s 15 is not, in my opinion, the single act or omission of failing to observe a general duty to maintain at all times a safe working environment for employees which may possess one or more of a number of characteristics or features, but each particular act or omission which amounts to a failure to maintain that environment. Each act or omission which constitutes a failure specified in s 15(2) or otherwise amounts to a breach of the duty under s 15(1) is, in my opinion, a separate offence under the section. I respectfully agree with the reasoning and conclusion of Fullagar J in Chugg v Pacific Dunlop Ltd [1988] VR 411 and Stanley P in Broken Hill Associated Smelters Pty Ltd v Stevenson [1991] 42 IR 130. 86 Also in the majority in Boral Gas v Magill on this aspect, I reasoned the issue in the following way (at pp 205-207; p 416) : On its face, my view is that s 15, in sub-s (1) creates but one offence, namely the failure of an employer to "ensure the health, safety and welfare at work of all his employees". Sub-section (2), in its terms, sets out a number and variety of ways in which that single offence may be committed; such ways, I emphasise, are put in the alternative so that any one of them, if made out, may constitute the single offence in sub-s (1), although if each be made out then the corresponding number of separate offences against sub-s (1) will be committed. … I view each of the lettered par (a) to par (f) in sub-s (2) as constituting separate and discrete means, albeit in some cases being in a similar fact situation, by which an employer may commit one or more separate offences against sub-s (1) and in respect of each of which separate charges would have to be made to avoid duplicity. … … The prime reason, however, for my view is in the very nature of the matters contained in the paragraphs in sub-s (2); they each represent significant and separate categories of conduct by an employer to ensure the stipulated condition of a safe workplace. Of course, a failure to observe any one of them will be a breach, but a multiple failure must surely lead to multiple breaches. If that were not so and only one breach was regarded as having occurred then, I think, the importance of one or other of the requirements would be negated. It would be a fortiori where each failure occurred at a different location at a workplace or, even at the same location, arose out of different circumstances. … 87 In the case here, as it was in Boral Gas v Magill , two contraventions are alleged of s 15(1) - first, a failure to provide a safe system of work; and, second, a failure to provide such information, instruction, training and supervision of employees as may have been necessary to ensure their health and safety at work. Whilst each offence related to the single act of measuring the contents of the bitumen tank on the spray tanker, each failure, in my view, was quite separate and distinct as concerning a different aspect. The point may be tested in this way: the defendant may well have established a perfectly safe system of work without risk but failed to adequately instruct or train its employees in that system; alternatively, the defendant may have properly and adequately trained its employees to perform their work safely but the actual practice at the workplace represented an unsafe system of work. If it were otherwise, then, it seems to me, the significance of the separate requirements as to, on the one hand, the system of work and, on the other hand, instruction and training, would be lost. 88 I am of the view, therefore, that the two charges in the present case relate to separate and distinct acts or omissions and, so, are capable of constituting two offences against s 15(1). Approach to the evidence 89 Whether the two subject offences have been made out depends upon the view taken of the disclosed facts as applied to the essential elements of each alleged offence. Whatever may be said of the disputed issues, particularly the scientific evidence, I am satisfied beyond doubt that the evidence established that at about 5.00 pm on 17 November 1994 at Blackneys Road, Stokers Siding the ignition of a flammable cloud of vapour occurred while Mr Newton, an employee of the defendant, was on the top of the defendant's bitumen spray tanker after measuring the contents of the tank with a dipstick through the open hatch in the course of his work. A fireball resulted which engulfed Mr Newton causing him severe burn injuries. 90 Of course, the occurrence of the fireball and the consequences for Mr Newton, without more, do not establish the relevant detriments to safety as contained in the charges; the relevant failure must be shown to be that of the defendant: see Cullen v State Rail Authority (31 IR at p 210). And as Fisher CJ commented in Boral Gas v Magill (37 NSWLR at p 157; 58 IR at p 367) - "There does not have to be an accident and/or injury to attract the attention of the Act, but in the majority of cases the dangers complained of come to light and are investigated in those circumstances". 91 In the present case, much of the physical evidence available at the time of the incident was either destroyed or modified by the conduct of the defendant. For instance, the defendant almost immediately following the fireball re-filled the tank with bitumen and kept it at 180oC for 10 hours, thus preventing inspection of the earlier level of bitumen and its nature, and modified the hatch on top of the tanker by replacing it with a new lid and seals; the overalls worn by Mr Newton at the time also were unavailable. Thus, the attendance by Mr Hannan on 18 November 1994 to investigate the circumstances was frustrated by that lack of physical evidence and so too were the subsequent inquiries on behalf of the inspector. It was that lack of physical evidence which led Professor Gray to conclude that it was not scientifically possible to determine what caused the fireball. Nevertheless, the evidence in the proceedings comprehended the accounts of eyewitnesses to what occurred at the time, reports compiled by the defendant as to what occurred, scholarly papers on fires involving bitumen tanks, the defendant's safety handbook, the Code of Practice for the Safe Handling of Bitumen Products produced by the Australian Institute of Petroleum and authoritative articles about the composition of bitumen, together with the accumulated experience of Dr Green in investigating bitumen fires. In my view, that evidence, circumstantial as it was, provided an available and proper basis to make findings and determine whether the essential elements of the charges were established. 92 It should immediately be remarked that it is far from unusual for the prosecution to be forced to rely exclusively on circumstantial evidence in order to obtain a conviction because if it had to do so then an offender could commit an offence with impunity provided care was taken to ensure no other person was present. Indeed, and as Jordan CJ, with whom Davidson and Street JJ agreed, said in R v Cable [1947] 47 SR (NSW) 183 at 184 - "In many cases, circumstantial evidence is stronger than direct evidence, which is subject to the fallibility of human observation and recollection." As to the use of circumstantial evidence, the Chief Justice in Cable (at p 185) referred with approval to the earlier decision of the Court of Criminal Appeal in R v Rothery [1925] 25 SR (NSW) 451 at 459 in which James and Campbell JJ agreed with these comments by Ferguson J : One contention very strongly urged upon us was that as the case was one of circumstantial evidence, and as there was evidence upon which the jury might reasonably have come to the conclusion that another person was responsible for the poisoning, the appellant was entitled to an acquittal. This contention was based upon a misconception of the rule relating to circumstantial evidence, that the circumstances should, to a moral certainty, actually exclude every hypothesis except that of guilt. But that is not a rule for determining whether evidence is to be believed or not; it has to do not with conflicting evidence, but with conflicting inferences which may be drawn from the circumstances, that is, from the facts proved by direct evidence . If, for example, on a trial for murder it is proved that the accused was seen coming out of the room of the dead man carrying a blood-stained knife, it is for the jury to say whether on the whole of the circumstances this fact is consistent with innocence. If evidence is given for the defence that the man seen with the knife was not the accused, that does not give occasion for applying the rule as to circumstantial evidence. It is then a conflict of direct evidence. If, upon weighing the evidence, the jury are satisfied beyond reasonable doubt that the accused was the man, they are not concerned with any inference, however cogent, that might be drawn from the evidence that he was not the man. (emphasis added) 93 Mr Simpkins submitted, consistent with what Jordan CJ said in Cable, that conviction should not occur unless the evidence was inconsistent with any other reasonable hypothesis (or explanation) than that the defendant was guilty; however, Mr Simpkins went somewhat further and added that where the evidence, as here, was largely circumstantial then the prosecutor in excluding any reasonable hypothesis consistent with innocence had to "prove all intermediate facts necessary for such a conclusion beyond reasonable doubt"; counsel relied for that proposition on Shepherd v The Queen (1990) 170 CLR 573. I have to express the view that I think counsel overstated the proposition. It is necessary to refer in this respect to what was said by Dawson J (with whom Mason CJ, Toohey J and Gaudron J agreed, and McHugh J to a similar effect) in Shepherd , as follows (at pp 579-580) : Circumstantial evidence is evidence of a basic fact or facts from which the jury is asked to infer a further fact or facts. It is traditionally contrasted with direct or testimonial evidence, which is the evidence of a person who witnessed the event sought to be proved. The inference upon the jury may actually be asked to make in a case turning upon circumstantial evidence may simply be that of the guilt of the accused. However, in most, if not all, cases, that ultimate inference must be drawn from some intermediate factual conclusion, whether identified expressly or not. Proof of an intermediate fact will depend upon the evidence, usually a body of individual items of evidence, and it may itself be a matter of inference. More than one intermediate fact may be identifiable; indeed the number will depend to some extent upon how minutely the elements of the crime in question are dissected, bearing in mind that the ultimate burden which lies upon the prosecution is the proof of those elements. For example, with most crimes it is a necessary fact that the accused was present when the crime was committed. But it may be possible for a jury to conclude that the accused was guilty as a matter of inference beyond reasonable doubt from evidence of opportunity, capacity and motive without expressly identifying the intermediate fact that the accused was present when the crime was committed. On the other hand, it may sometimes be necessary or desirable to identify those intermediate facts which constitute indispensable links in a chain of reasoning towards an inference of guilt. Not every possible intermediate conclusion in fact will be of that character. If it is appropriate to identify an intermediate fact as indispensable it may well be appropriate to tell the jury that that fact must be found beyond reasonable doubt before the ultimate inference can be drawn. But where - to use the metaphor referred to by Wigmore on Evidence, vol 9 (Chadbourn rev 1981), par 2947, pp 412-414 - the evidence consists of strands in a cable rather than links in a chain, it will not be appropriate to give such a warning. It should not be given in any event where it would be unnecessary or confusing to do so. It will generally be sufficient to tell the jury that the guilt of the accused must be established beyond reasonable doubt and, where it is helpful to do so, to tell them that they must entertain such a doubt where any other inference consistent with innocence is reasonably open on the evidence. As I have said, the prosecution bears the burden of proving all the elements of the crime beyond reasonable doubt. That means that the essential ingredients of each element must be so proved. It does not mean that every fact - every piece of evidence - relied upon to prove an element by inference must itself be proved beyond reasonable doubt. Intent, for example, is, save for statutory exceptions, an element of every crime. It is something which, apart from admissions, must be proved by inference. But the jury may quite properly draw the necessary inference having regard to the whole of the evidence, whether or not each individual piece of evidence relied upon is proved beyond reasonable doubt, provided they reach their conclusion upon the criminal standard of proof. Indeed, the probative force of a mass of evidence may be cumulative, making it pointless to consider the degree of probability of each item of evidence separately. (emphasis added) 94 Accordingly, as Dawson J observed in Shepherd (170 CLR at p 581) by reference to the earlier decision of the High Court in Chamberlain v The Queen [No 2] (1984) 153 CLR 521 - "It is, I think, quite plain that, in saying that a 'fact as a basis for an inference of guilt' must be proved beyond reasonable doubt, their Honours are referring to an intermediate fact which is a necessary basis for the ultimate inference". Finally on this aspect, Dawson J, I think, made it plain when he said (170 CLR at p 582) - "The inference referred to is clearly the ultimate inference of guilt and 'the circumstances from which the inference should be drawn' cannot, having regard to the first passage which I have set out, refer to each individual fact going to support the inference and must be a reference to any intermediate conclusion of fact required to be established before the ultimate inference can be drawn" and (at p 585) - "The judgments in Chamberlain do not support the proposition that, in a case resting upon circumstantial evidence, the jury may only properly draw an inference of guilt upon facts - individual items of evidence - proved beyond reasonable doubt." 95 I do not consider the decisions in Chamberlain and Shepherd support the broad proposition put by Mr Simpkins . I propose to apply the approach to the circumstantial evidence here in the manner referred to by Dawson J in Shepherd , that is, to first make findings of fact thereon and then to draw inferences therefrom as part of "strands in a cable rather than links in a chain", but with the ultimate inference as to the guilt of the defendant being satisfied only on the whole of the circumstances beyond reasonable doubt. It need only be added that where a particular intermediate fact constituted a necessary element in the establishment of the charge then that fact must be established beyond reasonable doubt. The system of work charge 96 The essential particular of the first charge as to an unsafe system of work was, in terms, that the failure was in respect of measuring the contents of the tank on the bitumen spray tanker. Further particulars were stated in Mr Hannan's affidavit, which was referred to in and annexed to the initiating summons, to the effect that the practice of purging bitumen spraylines with cutter (here Mexcut B) resulted in a small amount of cutter being forced into the bitumen tanks; thereby, as the affidavit stated, an explosive atmosphere was created in the heated bitumen tank which vaporised with air to form a highly volatile gas; and the top hatch lid had a damaged seal so as to permit the volatile gas to leak from it. It was noted also in the particulars that what occurred following the purging of the spray bars ("blowing the bars") was that Mr Newton proceeded to measure the contents of bitumen in the tank and to do so he mounted the top of the tanker, opened the hatch and used the dipstick. After closing and securing the hatch, he stood up and was engulfed in the fireball causing him severe burn injuries. The most likely cause of ignition of the volatile gas was said to be metal-to-metal contact occurring when Mr Newton closed the hatch due to part of the lid's seal being worn. 97 Dr Green concluded, for the reasons earlier outlined, that Mr Newton suffered injury because he was required to open the hatch to dip the bitumen tank; the opening of the hatch allowed a mixture of fuel and air to flow out of the hatch, exacerbated by the chimney effect, to form a flammable vapour cloud on top of the tanker which was subsequently ignited to form the fireball. Dr Green added that the Mexcut B sucked back into the tank, instead of being returned to the outside storage bottles, provided additional vapour in the tank of a volatile nature as the Mexcut B had not completely mixed with the bitumen to reach a state of equilibrium before the hatch was opened. 98 The conclusions reached by Dr Green as to the detriment to safety were, as I understand them, entirely consistent with the way in which the prosecution put its case. 99 However, Professor Gray regarded the practice of opening the hatch to dip the tank as placing the employee in potential danger from an explosive vapour as "largely wrong" and he disagreed with Dr Green's proposition that the practice of venting the bitumen tank created a potential uncontrolled hazard of an explosive atmosphere as being "quite wrong". Nevertheless, Professor Gray agreed with Dr Green that the fireball resulted from the ignition of a substantial release of flammable vapour. He was of the view that such vapour came from the LPG bottles located on the rear of the tanker, with the possible source of ignition being an electrical fault on the tanker's equipment (particularly the pump motor) or the hot surface on the pump, brakes or exhaust. Overall, Professor Gray's evidence was to the effect that Dr Green's scenario was an "interesting theory" but in the absence of physical evidence what occurred was "an unknown event". Significantly, Professor Gray discounted the source of ignition as being the pyrophoric deposits which were activated with the sudden rush of air when the hatch lid was opened. At the base of his opinion was the calculation of the contents of the bitumen tank as being incapable of forming a flammable cloud, said by him to be "scientifically trivial". 100 In reviewing the expert scientific evidence, it is helpful to consider the lay evidence and in the context of the various learned articles, the Code of Practice for Safe Handling of Bitumen Products, the critical incident report by Mr Skidmore, the accident report submitted by the defendant to the WorkCover Authority and the modifications made to the tanker following the incident. As a general proposition, it may immediately be said that all of that evidence supports the opinion expressed by Dr Green and not that of Professor Gray. Further, it may be emphasised, Professor Gray, as I have earlier remarked, displayed a somewhat incomplete knowledge of the fundamentals of the substances involved, particularly bitumen, and he discounted the various incidents expressed in the articles in the scholarly journals; of course, he conceded he had had no experience investigating bitumen fires and approached his task here by the use of ideal laws applied to scientific theory whereas, it is plain to me, the contents of the bitumen tanker, as Dr Green recognised, represented a complex mix of substances of a volatile and flammable nature. 101 Mr Hannan examined the tanker concerned on the day following the incident and noticed modifications made to the hatch seal and lid; no reference was made to any repairs to the LPG storage tanks. About 3 weeks before the incident, the Roads and Traffic Authority inspected the tanker and satisfaction was noted with its construction, including as to the heating tubes and burners as part of the system used to heat the bitumen in the tank using the LPG. The tanker was again inspected on 18 and 21 November 1994 by Mr McKenzie, a consulting engineer, at the request of the defendant and his report noted that "the explosion occurred after the top inspection hatch had been closed, causing a flash of ignited vapour to blow out through the seal at the rear side of the hatch"; he further noted the modifications made to the hatch lid and to the new hatch seals. 102 In his report, Mr Skidmore as the defendant's occupational health and safety adviser, although being unable to positively identify the ignition source, reported "the cause of creation of an explosive atmosphere within the tank has been established" and such atmosphere was created by "the Mexcut B when forced into the heated atmosphere of the tank with air vaporised and formed a highly volatile gas". Mr Skidmore made recommendations to prevent a recurrence of the incident and principally those recommendations included the checking of hatch seals whenever the hatch was open, dipping the tank prior to cleaning the spray bars to ensure no person was in the hatch area when flushing was undertaken, the tanker to be treated as flammable liquid transport and dipsticks to be located outside the hatch. Consistent with Mr Skidmore's report, the defendant's accident report to the WorkCover Authority noted the cause of the occurrence as "fire escaped through the hatch and came into contact with Newton"; the accident report detailed the steps taken to prevent the incident recurring. 103 Mr Anolek, the driver of the tanker at the time, inspected the top of the tanker after the fireball and saw, as he said, that the hatch cover "looks like it has blown out and it was landing up on top". Also, Mr Anolek said the defendant had since issued a notice for the tank to be dipped before the spraybars were blown. Significantly, having in mind Dr Green's evidence that Mexcut B injected into the bitumen in the tank would take about 30 minutes to mix and reach a state of equilibrium, Mr Anolek stated that the bars were blown about 5 minutes before Mr Newton opened the hatch. He agreed that during the process of "blowing the bars" some of the cutter entered the tank and mixed with the bitumen. Interestingly, however, Mr Anolek's evidence was that he did not think it mattered whether the bars were blown before or after the tank was dipped through the hatch. Also of importance in reviewing Dr Green's evidence, Mr Anolek said he noticed a small fire on top of the tanker after the incident and added that "the packing from around the hatch cover was laying on around the hatch and it was burning and there was a couple of pieces of cotton waste which we had been using to wipe the dipstick with that were burning". 104 Mr Newton confirmed he dipped the tank "the very next thing" after the bars were blown when Mr Anolek asked him to do so. He used a cotton waste cloth to wipe the dipstick during the dipping process and noticed before closing the hatch that some packing around the seal was hanging by a thread at one end and was worn at the other end; he poked the packing back into the slot and then closed the hatch. As to the fumes on top of the tanker, Mr Newton said he could not avoid breathing them because "they were everywhere". Like Mr Anolek, he said that during the process of cleaning the spray bars with cutter "its actually sucked back into the tank of the truck (where all the rest of the bitumen is), not pumped back into the container". 105 The defendant's Safety Handbook noted that "kerosene vapours are highly flammable and explosive" so that "during 'cutting' operations all flames and sources of sparks … must be eliminated". 106 The Code of Practice produced by the Australian Institute of Petroleum, as Dr Green acknowledged, attended to the hazards arising during the handling of bitumen and related products due to the high temperatures involved, the flammable nature of the products and possible presence of toxic materials or vapours; the guidelines set out in the Code were intended to eliminate potential hazards. I have set out earlier in these reasons relevant extracts from the Code and I do not repeat them. Suffice it to say that those extracts have, in my view, direct relevance for present purposes. For instance, in dealing with sources of ignition the Code referred to the need to avoid through-drafts of fresh air in tank vapour spaces by keeping hatches closed so that the self-heating and possible auto-ignition of carbonaceous deposits may not occur. As to the blending of cutters with bitumen, the Code noted the main danger as including the risk of fire or explosion so that during blending no source of ignition should be permitted within a distance of 15 metres of the operation. In noting that cleaning of pump hoses and tank pipework will be required after discharge of bitumen (eg blowing the bars), the Code stated that "cleaning solvents should not be discharged into bitumen storage tanks … a separate solvent storage facility should be established". As to access to bitumen tank tops, the Code said that such access by personnel "should be strictly regulated at all times … avoided as far as is reasonably practicable, during product movements into or out of the tank concerned" and should be prohibited "during the blending of cutback". 107 My view is that that material from the evidence is wholly supportive of the opinion expressed by Dr Green as to the detriments to safety in the present circumstances. The contrary view expressed by Professor Gray, I am satisfied, not only was not supported by such material but indeed was inconsistent with it. Further, I have expressed earlier some disquiet as to the apparent incomplete knowledge of Professor Gray with the fundamentals of the substances involved here, of his remote experience with bitumen, of the significance in the scholarly journals of case histories of incidents in heated bitumen storage tanks and of the Mathematical Model for the Self-heating of Deposits found in Heated Bitumen Storage Tanks. So too, his view that an operator, such as Mr Newton, in dipping a bitumen tank would not be exposed to a flammable atmosphere is against the evidence not only of Dr Green but also of the material contained in the Code of Practice and in the scholarly journals. Even though Professor Gray conceded that the guidelines contained in the Code of Practice were "sensible and reasonable" he nonetheless maintained his position that it had not been scientifically demonstrated that a flammable vapour cloud, other than from the LPG, was emitted through the hatch. On the whole of the evidence, I prefer that of Dr Green to Professor Gray to the extent there were differences. I accept the evidence of Dr Green. 108 I reject Mr Simpkins submission that the presence of LPG provided an alternative reasonable hypothesis for what occurred. Apart from the fact that LPG was present in the storage tanks, there was simply no other evidence to suggest that LPG was a contributing factor in any way to the circumstances of the flammable cloud on top of the tanker nor that there was any problem with leakage of LPG from the storage bottles. Indeed, that there was a problem with the LPG would be contrary to the evidence and against the results of the inquiry made by the defendant following the fireball; it made modifications to the hatch on the top of the tanker and changed the work practice of blowing the bars before the tank was dipped. In any event, the evidence of Mr Newton was clear in that he closed and secured the hatch after dipping the tank but, as Mr Anolek said in evidence, after the fireball he observed that the hatch cover "looks like it has blown out and it was landing up on top". 109 On the whole of the evidence, I am satisfied beyond a reasonable doubt the existence at the relevant time on 17 November 1994 at Blackneys Road, Stokers Siding of a detriment to the safety of the defendant's employees, particularly Mr Newton, operating the bitumen spray tanker by reason of an unsafe system of work. That unsafe system involved the opening of the hatch on top of the tanker, shortly after the cleaning of the spray bars with cutter and the flowback of cutter into the tank, so as to enable the contents of the tank to be measured with a dipstick thereby enabling the release through the open hatch, assisted by the chimney effect, of a flammable vapour cloud which engulfed Mr Newton. Although the source of ignition was uncertain, the offence was complete as soon as the flammable vapour cloud existed on the top of the tank causing a potential hazard to a person, such as Mr Newton, in that position. The ignition of the fireball by some means, likely to have been an electrical fault on the tanker or the activation of contaminated pyrophoric material, was merely the causa causans of the fireball whereas the detriment to safety in breach of s 15 of the Occupational Health and Safety Act was the causa sine qua non being the system of work so permitting the opening of the hatch in such circumstances. 110 As to the s 53 defence, my view in the circumstances of this case is that it cannot be separated from the conduct of the defendant in laying down the system of work. After the fireball occurred the defendant took steps to remedy the identified detriment to safety - the measuring of the contents of the tank by use of the dipstick through the open hatch was to occur before cleaning of the spray bars, dipsticks were to be located outside the hatch, hatch seals were to be checked when the hatch was opened and the hatch lid was to be lowered slowly and not dropped; all areas around the bitumen tanker to be declared mandatory non-smoking areas and the tanker was to be signed as "flammable liquid transport". Those measures, as Dr Green suggested, would have avoided the present risk to safety and they were all reasonably within the control of the defendant to implement. I am well satisfied that the defendant failed to establish that it was impracticably for it to so provide. The s 53 defence must fail. 111 I find that the charge relating to the unsafe system of work has been established. The instruction and training charge 112 The prosecutor alleged that the defendant failed to provide such information, instruction, training and supervision of its employees as necessary to ensure their health and safety in respect of measuring the contents of the bitumen tank on the spray tanker. In particular, it was claimed that Mr Newton did not receive from the defendant any appropriate direction in his task apart from being provided with the safety booklet to read. 113 Mr Anolek's evidence was to the effect that employees operating bitumen tankers for the defendant were shown how to do so by "qualified people" and that they were advised of various risks to be avoided such as smoking, lamps burning while spraying bitumen, naked flames and parking under power lines; as he said, "that is pretty much about it". Specifically as to the procedure for dipping the tank, Mr Anolek said the defendant did not advise anything in that respect; he agreed there was not really "any information or instruction or training in connection with the chances of the explosion when the hatch on top of the tank is open". Mr Newton, as to training received by him in dipping the tank, responded he had received "very little training, sort of, like, you stand on the ground and you watch from the ground and you never actually got up there with anyone to do it who got to show you. You just stood on the ground and watched them from the ground". Apart from seeing it done, Mr Newton agreed he did not attend any classes or lessons in how to do it. Mr Newton was not informed by the defendant about any danger from fumes coming out of the top of the tank through the hatch and he was not given any written guidelines or information as to the steps to take when measuring the tank with the dipstick. However, he did agree he had received training in the operation of the tanker at the depot but that that was with a "cold" tanker as part of testing by the Roads and Traffic Authority. 114 The defendant's supervisor, Mr Brown, confirmed the position as to training at the depot in the use of the dipstick as part of testing, but using cold products where no danger occurred, by the Roads and Traffic Authority. His evidence did not attend directly or at all to answering Mr Anolek's and Mr Newton's evidence that there was no instruction to prevent opening the hatch on top of the tanker shortly after the bars were blown. Somewhat surprisingly, I think, Mr Brown gave further evidence that following inquiries by the defendant and the consideration of a number of suggestions for changed work practices in the operation of the tanker, the procedure on-the-job was still the same as before the explosion. 115 The essential element of this charge was the failure by the defendant to instruct and train employees to the extent necessary to ensure their health and safety in the measuring of the contents of the bitumen tank. Having in mind the identified detriment to safety here, the evidence of Mr Anolek and Mr Newton satisfied me beyond doubt that such instruction and training did not occur. In a very real sense, my view is that the defendant was simply unaware of the risk involved to its employees and, so, did not provide appropriate instruction and training to avoid such risk. It was well within its power and control to do so. The defendant, in my view, did not make out the s 53 defence to this charge. 116 I am satisfied to the requisite standard of criminal proof that the instruction and training charge has been made out. Findings and future proceedings 117 For the foregoing reasons, I find the two subject offences proven as charged. 118 Submissions on penalty and costs will be heard on a date to be fixed by arrangement with the parties. _____________________ DISCLAIMER - Every effort has been made to comply with suppression orders or statutory provisions prohibiting publication that may apply to this judgment or decision. The onus remains on any person using material in the judgment or decision to ensure that the intended use of that material does not breach any such order or provision. Further enquiries may be directed to the Registry of the Court or Tribunal in which it was generated.