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.