Industrial Relations Commission of New South Wales in Court Session CITATION : Rodney Dale Morrison v Coal Operations Australia Limited [2003] NSWIRComm 249 PROSECUTOR Rodney Dale Morrison PARTIES : DEFENDANT Coal Operations Australia Limited FILE NUMBER: IRC6726 and 6727 of 2001 CORAM: Peterson J CATCHWORDS : Occupational health and safety - Roof fall in coal mine - Employee killed - Fall during roof bolting procedures - Whether employer protected by s33 of OHS Act in relation to acts or omissions expressly authorised by associated legislation - Coal Mines Regulation Act 1982 and Coal Mines Regulation (Support - Underground Mines) Regulation 1984 - Roof fall not able to be anticipated with any certainty - Defence held made out - Whether offence otherwise under s15(1) - Found not guilty. LEGISLATION CITED : Occupational Health and Safety Act 1983 Coal Mines Regulation Act 1982 CASES CITED : Rodney Morrison v Tahmoor Coal Pty Limited [2001] NSWIRComm 327, 3 December 2002 (unreported). HEARING DATES: 02/10/2003; 02/11/2003; 02/12/2003; 02/13/2003; 02/14/2003; 02/17/2003; 02/18/2003; 02/19/2003; 02/20/2003; 02/21/2003 DATE OF JUDGMENT: 08/15/2003 Mr S Crawshaw SC with Mr P Ginters of counsel SOLICITOR Crown Solicitor's Office SYDNEY. LEGAL REPRESENTATIVES: DEFENDANT Mr B D Hodgkinson SC with Mr M L Shume of counsel SOLICITOR Sparke Helmore SYDNEY. JUDGMENT: - 11 - INDUSTRIAL RELATIONS COMMISSION OF NEW SOUTH WALES IN COURT SESSION CORAM: PETERSON J DATE: 15 AUGUST 2003 Matter No. IRC6726 of 2001 RODNEY DALE MORRISON v COAL OPERATIONS AUSTRALIA LIMITED Prosecution under s 15(1) of the Occupational Health and Safety Act 1983 Matter No. IRC6727 of 2001 RODNEY DALE MORRISON v COAL OPERATIONS AUSTRALIA LIMITED Prosecution under s 15(1) of the Occupational Health and Safety Act 1983 JUDGMENT 1 Rodney Dale Morrison is a person authorised by the Director General of the New South Wales Department of Mineral Resources, a prescribed officer pursuant to s106 of the Occupational Health and Safety Act 2000 ('the 2000 Act') to commence a prosecution in relation to alleged offences under the Occupational Health and Safety Act 1983 ('the 1983 OHS Act') in coal mines. 2 The defendant, Coal Operations Australia Limited, is a coal mining company which in 1998 was operating the Wallarah Colliery at Crangan Bay in the south-eastern corner of Lake Macquarie. The Wallarah Colliery was then mining part of a substantial seam of coal running in an approximately south-east - north-west direction called the Great Northern Seam. As the evidence will demonstrate, the Great Northern Seam is marked by a layer of conglomerate, which occurs there between seams of coal. The mining is undertaken under the layer, known as Teralba conglomerate, that layer forming the roof under which the miners work. It is generally supported by the insertion of 1.4m long roof bolts, which are inserted into holes drilled by machine intended to secure the roof by pinning the immediate area of the roof to the strata above it. 3 On 6 July 1998 an accident occurred at the mine, in which a section of the roof fell in a heading (a horizontal mining shaft), causing fatal injuries to a coal miner, Anthony James Carroll and pinning by the legs another miner, Tony Ian Dixon. The roof fall occurred while the miners were engaged in drilling the roof to secure it with roof bolts. While the conglomerate roof in the Great Northern Seam has commonly exhibited generally a solidity and strength, the fall in this case appears to have been caused by the existence of an undetected horizontal fault in the layer consisting of a clay-like matrix between layers of conglomerate. 4 The defendant has been charged with two offences under the 1983 OHS Act, both against s15(1), essentially in relation to the system of work involved in rock bolting the roof to make it safe and the means adopted of testing the roof for stability. The defendant has pleaded not guilty in respect of each charge. 5 The charges, and the particulars thereof are as follows: IRC6726 of 2001 On 6 July 1998, at the Wallarah Colliery, Crangan Bay, Nords Wharf, in the State of New South Wales, the Defendant, being an employer, failed to ensure the health, safety and welfare at work of all its employees, in particular, Anthony James Carroll and Tony Ian Dickson, in that it failed to provide or maintain systems of work that were safe and without risks to health contrary to section 15(1) of the Occupational Health and Safety Act 1983 . Particulars a) There was a potential risk to the health, safety and welfare of the employees working in the vicinity of the area described as Face area sequence 131, Production Panel 3 in Production District 3 on 6 July 1998 in that there was risk of a roof fall while the employees were working there; b) The Defendant's failure and/or omission was the failure and/or omission to provide or maintain adequate systems of work that were safe and without risks to health in relation to the erection of roof support in the vicinity of the area described as Face area sequence 131, Production Panel 3 in Production District 3 in circumstances where roof bolting was to take place; c) There was a causal connection between the risk to the health, safety and welfare of the employees referred to in (a) above and the Defendant's failure and/or omission as dealt with in (b) above. IRC6727 of 2001 On 6 July 1998, at the Wallarah Colliery, Crangan Bay, Nords Wharf, in the State of New South Wales, the Defendant, being an employer, failed to ensure the health, safety and welfare at work of all its employees, in particular, Anthony James Carroll and Tony Ian Dickson, in that it failed to provide or maintain systems of work that were safe and without risks to health contrary to section 15(1) of the Occupational Health and Safety Act 1983 . Particulars a) There was a potential risk to the health, safety and welfare of the employees working in the vicinity of the area described as Face area sequence 131, Production Panel 3 in Production District 3 on 6 July 1998 in that there was risk of a roof fall while the employees were working there; b) The Defendant's failure or omission was the failure and/or omission to provide or maintain adequate systems of work that were safe and without risks to health in relation to assessing the stability of the roof structure in the vicinity of the area described as Face area sequence 131, Production Panel 3 in Production District 3; c) There was a causal connection between the risk to the health, safety and welfare of the employees referred to in (a) above and the Defendant's failure and/or omission as dealt with in (b) above. 6 It will be seen from the particulars that IRC6276 of 2001 is concerned with a failure and/or omission, as described, in relation to the erection of roof support and IRC6727 of 2001 is concerned with a failure and/or omission, as described, in relation to assessing the stability of the roof structure. The Coal Mines Regulation Act 1982 7 Coal mining operations are conducted under the statutory framework established by the Coal Mines Regulation Act, 1982. That Act ('the CMR Act') provides a comprehensive structure related to the safe conduct of coal mining operations. As to administration, it provides for the appointment of Inspectors of Mines with appropriate qualifications; the creation of the Coal Mining Qualifications Board, the functions of which include the determination of relevant qualifications for certificates of competency and the testing of applicants. Provision is made for the granting of certificates by the Minister, on the recommendation of the Board, to persons to be employed (relevantly) as a Manager, Under Manager, Deputy of a Mine or a Mine Surveyor. The CMR Act deals extensively with the duties of owners of mines and the functions of Managers, Deputy Managers, Under Managers and Mine Deputies. Generally speaking, these persons, referred to in the statute as mine officials, are responsible for, amongst other things, the safe operation of the mine. 8 The CMR Act provides in Part 2, Division 4, for a procedure under which certificates of competency may be suspended or cancelled by a Court of Coal Mines Regulation (constituted under s150) in circumstances where the Chief Inspector of Coal Mines has formed the opinion that the holder is unfit to hold the certificate because the person has, by reason of incompetence or negligence, caused injury to any person or property or is reasonably likely to cause such injury. 9 The high level of concern expressed in the CMR Act for safety is also illustrated by the provisions in Part 4, Division 2, s.71 for the election at each mine of two persons who are practical miners as "check inspectors for the mine". Their purpose is to enable inspections to be carried out at the mine on behalf of the persons employed there. At least one of the persons elected in respect of a mine shall be employed at that mine. Section 73 provides the powers of check inspectors as including a right to "be allowed to inspect the mine". Without limiting the generality of that provision, a check inspector for a mine may: 73(4)(a) at any time go into and inspect the shafts, roadways, working places, old workings and machinery and equipment at the mine, (b) inspect any documents or plans which by virtue of this Act or the regulations are required to be kept at the office of the mine, (c) where there is at the mine an accident or other occurrence (being an accident or occurrence for which notice is required by or under this Act to be given), inspect the place where the accident or other occurrence happened and, so far as is necessary for the purpose of ascertaining its cause: (i) inspect any other part of the mine and any machinery, apparatus or other thing thereat, and (ii) test the atmosphere at the place where the accident or other occurrence happened. 10 By s74 the manager of a mine and all other persons at the mine are required to afford "every facility and assistance to a check inspector for the purposes of an inspection of the mine by the check inspector". 11 Section 77 provides the district check inspectors with powers of inspection and, importantly, in the circumstances set out in s77, which principally involve a danger to the safety or health of persons employed at a place at the mine, a direction that any operations being carried on at the place be suspended. A mining official at the mine who received such a direction must forthwith comply with it. 12 As to the management of mines, Part 3, Division 1 of the Act deals with the functions and duties of mine officials and owners. By s32 the owner of a mine must make provision and take steps necessary to ensure that the mine is "so planned, laid out and equipped as to enable it to be managed and worked in accordance with this Act, the regulations, the rules and any schemes and any directions, or conditions of exemptions or approvals, given thereunder, and the mine is so managed and worked". 13 By s33, the manager of a mine may only appoint a person whose functions "will involve the issuing of instructions with respect to the management or working of the mine, which instructions relate, either directly or indirectly, to the safety or health of persons employed at the mine" only if the manager is "satisfied that the person has the knowledge and experience to recognise any present or potential danger associated with the operations to be carried out at the mine". 14 As to mine deputies, s42 requires the manager of an underground mine to appoint "such number of deputies as is sufficient in the manager's opinion to carry out efficiently the functions at the mine conferred or imposed on deputies by this Act, the regulations, the rules and any schemes and any directions, or conditions of exemptions or approvals, given thereunder". 15 The methods or systems of working mines are referred to in Part 5, Division 2 of the Act. By s138 "no method of mining, other than the bord and pillar system shall be used except with the approval of the Minister given on the recommendation of the Chief Inspector". In the bord and pillar system the pillars are to be of such dimensions as may be prescribed and the width of the roadways, bords, cut-throughs, headings and pillar splits shall not exceed the prescribed width, although the Chief Inspector may approve or direct a variation in the dimension of pillars etc. 16 Part 4, Division 7 of the CMR Act provides for the making of rules and schemes and, importantly, in s102 for rules to be known as "support rules". These are concerned with the support of the roof and sides of working places and roadways in the mine. 17 Section 105 of the Act requires the manager of a mine to send to the district inspector, within seven days of their making, a copy of the support rules or any alteration of them. The district inspector must, within 28 days of the receipt of the rules, serve on the manager a notice confirming the rules or alteration or, pursuant to s106, require changes as may be specified in a notice to be served on the mine manager. 18 Section 107 allows an appeal by the mine manager from the district inspector to the Chief Inspector who, within 21 days, must revoke, vary or confirm the notice appealed against. From the Chief Inspector's decision, an appeal lies to the court (s108). 19 Further guidance with respect to support rules is given to mine officials by the Coal Mines Regulation (Support - Underground Mines) Regulation 1984. Part 2 - Support - General Provisions provide relevantly for present purposes the following: Support for travelling roadways and working places 6. The person for the time being in charge of a part of a mine shall ensure that the roof and sides of every travelling roadway and working place in that part of the mine are secure in accordance with the support rules for that mine. Unauthorised entry to improperly supported areas prohibited 7. A person shall not enter upon a travelling roadway or work in a place within a mine which is not secure in accordance with the support rules for the mine unless that person has been authorised (by some person who is qualified, under the Act, to give that authority) to do so for the purpose of exploring or repairing. Temporary supports 8(1) Where a worker cannot forthwith erect a permanent system of roof support in a part of a mine safely and in accordance with the support rules for the mine, that worker shall erect temporary supports in that part for the purpose of ensuring the safety of any persons in that part until such time as permanent supports can be erected. (2) The person for the time being in charge of any part of a mine shall ensure that, where permanent supports cannot be erected forthwith in any place in that part, the workers in that place shall erect temporary supports to ensure the safety of any persons in that place. Withdrawal of support by safe means 10. A person shall not withdraw support from the roof or sides of any place in a mine otherwise than by a method or device by which that person does so from a position of safety. Appropriate withdrawal of certain support 11. Where it is part of a system of mining at a mine to withdraw support from the goaf or from under the roof adjoining the goaf, a person shall not, otherwise than in accordance with a system specified in the support rules for the mine, withdraw that support. Voluntary setting of additional supports 12. Nothing in this Regulation shall be construed as preventing a person from setting supports in the person's working place in a mine at more frequent intervals than those specified in the support rules for the mine. Means of setting support 14(1) A person building a chock or setting a prop which is to form part of a system of support in a mine shall build or set it on a proper foundation and make it tight to the roof. (2) A person using roof bolts to form part of a system of support in a mine shall ensure that the roof bolts are securely fixed in place. 20 As at 6 July 1998 Wallarah was operating under support rules for first workings in the Great Northern Seam at Wallarah Colliery, which had been signed off by the Colliery manager on 8 December 1997 and by the then District Inspector of Mines on 9 December 1997. 21 The minimum support rules contained, as required, both diagrammatical illustrations of the positioning of test holes, roof bolts and temporary roof support (brattice props) and also the following written rules: Great Northern Seam Minimum Support Rules Required for Remote Control Miner 1. During face advancement, a test hole is to be drilled at 3m centres at any place across the roadway, with a minimum depth of 0.9m. As appropriate, temporary support may be placed (at maximum 3m intervals) until such times a test hole is drilled. 2. The maximum distance of exposed roof beyond the last test hole or temporary roof support, to the face shall be 10m. 3. Workmen are not to proceed beyond the last test hole or temporary support unless the roof has been tested by sounding with a metal bar or suitable metal object & found secure. 5. Four way intersections are to have a minimum of 5 bolts, a minimum of 1.0m in length, located in similar positions as shown in the diagram. ie; One bolt in each quadrant & one in the approximate centre. This shall be completed immediately after the formation of the intersection. 6. A mining official may direct that additional support above the described minimum rules be installed when roof conditions deteriorate. 7. Roof Supports are to be installed to resin installation standards as displayed by the manufacturer. 22 The minimum support rules refer to "temporary support (brattice prop)" in describing a line of props running along one side of the heading at 3 metre separations. A brattice prop is a timber prop of the kind which, on the evidence, has two purposes. The "brattice" is the screening material which is hung from the brattice props to provide a wind tunnel or corridor to deliver fresh air to the area of mining, thus eliminating or limiting the effect of any gases experienced in the mining process. While the brattice props remain in place they perform the second function of supporting the roof in their locality. 23 Somewhat oddly, however, the minimum support rules do not identify, at least pictorially (and in this respect I think the rules are superficially misleading), the fact that temporary roof support, consisting of the same props utilised for the brattice, is used in supporting the main portion of the heading pending the bolting of the roof. 24 My reference to the support rules being misleading relates more to the uninitiated observer's reaction to them rather than the understanding of miners. The evidence is clear that members of the mining crew must not, and do not, walk beneath a roof which is unsupported (that is, not supported either by the use of temporary support in the form of timber props or having been roof bolted) unless there has been a sounding of the roof, which is found to be secure (rule 3 of the minimum support rules). The Evidence 25 A number of matters are not in dispute: the authority of the prosecutor; the defendant being the operator and part-owner of the Wallarah Colliery and an employer of employees, in particular Messrs Carroll and Dickson. 26 The evidence establishes a number of other matters which are really not in dispute. After the continuous miner has mined a particular area, the area is a "no-go" zone for staff engaged in the mine until the roof has been tested and/or supported. That support will consist of either temporary support in the form of timber props or permanent support by way of roof bolting. 27 The number of bolts to be inserted in the roof must conform, as a minimum, with the minimum support rules. It is a matter for the discretion of the miners as to whether a greater number of bolts are utilised. That determination will be made by the miners including the deputy according to the conditions of the roof as experienced and relying on the knowledge and experience of the deputy and the miners involved. 28 The condition of the conglomerate roof at Wallarah roof is variable. The standard means of testing the roof is to strike it with a length of drill steel in a process called "sounding the roof". A solid ring will be accepted as indicating a sound roof whereas a hollow or flat sound induced by the steel will indicate a "drumminess" of roof, perhaps inducing an increase in the number of bolts applied to the roof. 29 The concept of roof bolting is something I have had some difficulty grasping. The process is to drill a hole of the same length as the roof bolt, namely 1.4 metres, and to then insert the bolt together with a chemical which will set the bolt in the drill hole. The idea seems to be to "pin" the immediate layer of conglomerate forming the roof to the layer or layers above. I do not consider it has been explained in evidence sufficiently for present purposes for me to appreciate how this is accepted in the industry as providing a secure roof. I intend to act upon the basis that the acceptance is justified. That view is adopted in circumstances where the case revolves around the techniques employed in achieving the bolting process rather than the ultimate efficacy of the process itself. 30 The drilling machine utilised in Panel 3 at Wallarah at the time was a rotary percussive drill known as a Falcon Roof Bolter. While the drill is sometimes referred to as a "hand-held" drill, the drill sits on top of a telescopic leg which extends by hydraulic action to push the drill machine up to the roof. The drill, the drill steel having been loaded into the top of the machine, is then operated by a control lock or lever. 31 Abnormalities in the conglomerate layer are also detectable in the drilling process, from the condition of the product of the drill hole, and the presence of any water. Holes may be drilled as test holes and, in theory, left unfilled if they reveal no problem in the roof. The evidence was that the practice of the miners at Wallarah, however, was to utilise a roof bolt in all test holes regardless. 32 At about 11pm on 5 July 1998 Messrs Carroll and Dickson commenced work as members of a mining crew also comprising a deputy, Ken Tytherleigh and miners, Noel Pezely and Russell Anslow. 33 Their task was to undertake mining utilising a continuous miner and shuttle cars to transport the coal cut by the continuous miner back to the conveyor. They were working in the South-West Panel of Wallarah at cut-through 2 ("CT2") in B Heading in Number 3 Unit. According to the Work Sequence Programme, this was Sequence 131, Production Panel 3 in Production District 3. 34 Mining could not be immediately undertaken at the CT2 intersection with B Heading due to the presence of water, which it took about 90 minutes to pump out. Mining commenced at approximately 1.15am on 6 July 1998. 35 Approximately 16 shuttle cars of coal were mined before the continuous miner hit a fault in the coal seam. As the mining had progressed, the miner had come closer to the fault, which was running at a shallow angle in towards B Heading on the right hand side of the miner. At this point, the miner had progressed into B Heading beyond the point at which 3 cut-through would eventually be created, according to the mining plan. 36 The Under Manager on the shift was Ronald Wallace. He attended at the mining point upon becoming aware of the fault having been struck. He inspected the area with Mr Tytherleigh. They made certain observations of coaltops (residues of coal attached to the roof) and water coming out of the roof towards the left hand side of the heading. A sounding of the roof indicated that it sounded good. 37 Mr Wallace deposed that upon sounding the roof it had a "good ringing sound. It sounded very competent". He said that he instructed Mr Tytherleigh that they would cease mining and that he wanted "extra support put up, plus a row of props along the edge of the fault, and then I wanted the area taped off". 38 They then discussed where 3 cut-through would "hole through". It was measured and discovered that they were at that very point. They decided to square up the end of the heading before finishing. 39 Mr Wallace testified that he told Mr Tytherleigh that the extra support would be a double row of bolts with props along the edge of the fault. 40 Mr Tytherleigh had no recollection of that instruction having been given by Mr Wallace although he said it was possible. The other members of the crew did not give any evidence of Mr Tytherleigh instructing them to undertake that work. 41 I note that Mr Wallace claimed he had told Mr Tytherleigh not to work under unsupported roof and that he had told Mr Dickson the same thing. However, he agreed that it was not possible to carry out such orders with the equipment available without working under unsupported roof. 42 Messrs Carroll and Dickson then had crib break. The continuous miner was flitted (removed) from the face and bolting in B Heading then proceeded. Up to this time the normal pattern of bolting with single bolts 3 metres apart had been undertaken. Mr Wallace testified that he ordered the bolting to occur thereafter at 1.5 metre spacing. 43 Messrs Anslow and Pezely drilled and bolted two holes while Messrs Dickson and Carroll returned from crib. Water was coming out of the roof from the bolt holes. The drill steel was also jamming which was indicative of a poor roof. 44 Upon the return of Messrs Carroll and Dickson from their crib break Mr Anslow told Mr Dickson that he had noticed a parting (evidence of a soft layer in the conglomerate) in the hole they had just drilled. Messrs Carroll and Dickson then took over the bolting. They inserted a bolt in the hole which had just been drilled and then found that the air pressure in the Falcon roof bolter was limited. Messrs Tytherleigh, Carroll and Dickson proceeded to check the hoses supplying the air. Whilst doing this another fall occurred in the area of the face. This consisted of approximately 6 metres of stone. The roof had fallen back from the face to a point about 1.5 metres from where the last roof bolts had been installed. 45 After the fall the roof was sounded and still sounded competent. While Messrs Carroll and Dickson were drilling the last hole, Mr Dickson noticed a parting in this hole and the drill steel became jammed. Mr Carroll then attempted to free it either by striking it with another steel or pulling at it which was a normal way of freeing drills that were jammed at the mine. 46 At this point, Messrs Carroll and Dickson were working approximately 1.2 metres away from the last roof bolt they had inserted, which was the nearest support of the roof. 47 I am not able to accept the suggestion in the evidence of the Mine Surveyor, Mr Lord, that there was timber support in this vicinity. The suggestion is contrary to the evidence of those members of the mining crew who were present at the time. 48 It was while Mr Carroll was attempting to free the jammed drill steel that the roof fell, burying Mr Carroll and causing him fatal injuries and pinning Mr Dickson by the legs, which sustained multiple fractures. The Expert Evidence 49 Dr Russell C Frith, B.Eng (Hons), Ph.D. the Managing Director and Principal Engineer of Strata Engineering (Australia) Pty Ltd, Consultant and Research Engineers, was commissioned by the prosecutor to assess the mining and geo-technical influences relating to the fatal fall of ground at Wallarah Colliery on 6 July 1998. Dr Frith's Honours Degree was in mining engineering and his Doctorate in coalmine rock mechanics. Dr Frith inspected the site in company with Inspector Ryan on 9 July 1998. Mr Yates, the District Check Inspector, accompanied them. Dr Frith utilised the results of that inspection and also anecdotal evidence as to the events leading up to the two roof falls which he obtained from mine site personnel in making his assessment. The summary of his written assessment is as follows: Summary Having conducted an inspection of the roof fall site and surrounding areas, been made aware of the mining sequence leading up to the falls and also been informed of observations made regarding roof behaviour during the period in the shift leading up to the two roof falls, the following summary points are made: · The two roof falls occurred in the unsupported cut-out which had yet to be supported with primary roof bolts. · The second roof fall was cleanly truncated at the last line of installed roof bolts, indicating that the primary roof support used was adequate in stabilising the roof for the fall profile that occurred in the prevailing circumstances · The mining process in the area of the falls contained no obvious significant anomalies in that: Þ The cut-out length was within normal mining practice Þ The cut-out was not left unsupported for an extended period of time, over and above normal mining practice Þ The roadway width was within normal mining practices Þ The use of a rotary-percussive Falcon roof bolter was normal mining practice at Wallarah Colliery · The area of the two roof falls contains two localised geological features that can be individually linked with reduced roof instability: Þ A thin zone containing a highly disturbed coal: conglomerate contact which in places results in that contact being sub-vertical and also polished/slicken-sided in nature. The zone runs essentially parallel with the left-hand rib side in the area of the two falls and first enters the roadway from the right-hand rib a short distance outbye the falls. Þ There is evidence that the conglomerate roof in the area of the falls contains clay-like cementing in places. Such material is evident in places around the top of the cavity left by the roof falls. Both of these geological features may be related in some way to the main fault zone and it is recommended that the opinion of an expert structure geologist is sought on this aspect. The actual propensity for either aspect in other areas of the mine is not known. However, the combination of the two in one location would be expected to result in a significant reduction in roof stability (all other factors being equal), especially in an area yet to be supported with primary roof bolts. · Several physical phenomena occurred both before and after the two roof falls that can be linked to a reduction in roof stability as compared to other areas: Þ Ground water emanating from roof bolt holes Þ Jamming of drill steels during bolt hole drilling at around the 450mm to 600mm roof horizon Þ Guttering along one rib side after the cut-out was completed. Þ The increased loading of props set for brattice on the inbye side of where the zone of disturbed coal: conglomerate contact first appears in the roadway. The fact that the wetness of the roof and the loading of the brattice props changes markedly inbye the location that the zone of disturbed coal: conglomerate contact first appears in the roof, is very strong evidence as to its fundamental role in reducing overall roof stability in the area of the two roof falls. Overall, it is summarised that the probable cause of the two roof falls in the unsupported cut-out prior to primary roof support being installed was the occurrence and interaction of both a sub-vertical discontinuity along one rib line as well as a separation in the roof through the vertical tensile failure of a thin zone of conglomerate. The influence of a clay-like matrix in locally weakening the conglomerate and allowing separation to occur is strongly implied. Both of these features could be linked in some manner to the main fault system present in that area of the mine. Whilst either effect could occur in isolation and not necessarily result in a roof fall situation, it is assessed that the presence and resultant interaction of both effects would almost certainly result in a roof fall occurring in any section of unsupported roof. Therefore, the fact that two roof falls occurred in an area of the mine effected by both phenomena is an understandable outcome. 50 The prosecutor also tendered a report by Dr Konrad H.R. Moelle, D.Phil., F.Aus.I.M.M. Dr Moelle passed away in the period between the finalisation of his report and the trial. The report was tendered without objection. Dr Moelle's conclusions were as follows: Mr A Carroll was, in the opinion of the present author, killed by a dislodged slab of Teralba Conglomerate that parted from the roof suddenly, probably without any warning and along an existing near horizontal parting in the conglomerate rockmass overlying the Great Northern Seam. The vertical or sub-vertical delineations of the slabs are by joint surfaces and, by what appear to be mining induced, fracture surfaces. The falling slab did most likely part from the immediate roof without much or any warning before it could be bolted to the overlying section of the conglomerate. The conglomerate consists of pebbles in the size ranges of 8cm x 4cm, 3cm x 1.5cm and smaller. The pebbles are rounded to sub-rounded and show a preferred orientation according to dimension. The cement of the conglomerate consists of low temperature secondary quartz (SiO2) . It is probable, in the present author's opinion, that the free water in the roofstrata has contributed to the failure by modifying pore pressures, providing water molecules to enter the lattice structure of some clayminerals and by chemically altering zeolites that had crystallized on the surfaces of joint sets and also on the partings that represent "depositional layering" surfaces. It is also probable, in the present author's opinion, that the vibrations generated by the hand-held Falcon roofbolter and associated activities, have contributed also to the sudden parting of conglomerate slabs during the ongoing bolting work process. Bolting operations under erosional Teralba Conglomerate are evidently best conducted with bolting machinery that allows the operator to be under supported roof at any time. The well developed preferred orientation of pebbles by their long dimensions in the Teralba Conglomerate probably contributed to drilling difficulties that may have been experienced by the accident victims in this case. The preferred orientation of the pebbles frequently causes the tips of some pebbles to protrude into the drilled hole, impeding the "smooth" progress and withdrawal of the drill rod. A dense conglomerate fabric with a strong and predominantly siliceous cement, like the Teralba Conglomerate at the site under investigation, would probably be subjected to relatively strong vibrations generated by the Falcon roofbolter, as the bit would not cut into the rockmass steadily, but more likely in an intermittent progress fashion. Whereas some pebbles in the path of the bit would slow down its progress, other pebble lithologies would offer considerably less resistance. It is thus conceivable, that the magnitude and intensity of vibrations generated during the bolting work process varied, possibly even in a fashion slightly resembling cyclicity. In the opinion of the present author, it is likely, that the action of the continuous miner driving the B-Heading resulted in the opening of some joints and siliceously healed microcracks in the conglomerate, as well as in the formation of mining induced fractures. Subsequently moisture levels in the conglomerate increased by water migration along joints, fractures and cracks. Chemical reactions commenced in minerals susceptible to chemical alteration and bonding commenced to deteriorate. An adjustment process, involving movement in the micro-domain and some physical settlement of the conglomerate body followed resulting in the development of gradually increasing shear stresses in the existing joint sets and the generally horizontal partings. The bolting operations, in progress at the time of the accident, which would have prevented the continuation of the disintegration and loss of cohesion in the conglomerate, was evidently too late. It is very difficult, in the opinion of the present author, to determine the length of the described deterioration processes, particularly if the presence of horizontal partings is not always recognised. The setting of temporary timber props serving as indicators for roof adjustment movements should be considered under Teralba Conglomerate roof, as well as the use of remotely controlled bolting devices. 51 Dr Frith's evidence in cross-examination dealt with the known testing procedures for conglomerate roof as principally incorporating a patterned sounding of the roof with a hammer so that, according to the sound the roof made, the individual would make a judgment as to whether the roof was stable or potentially unstable. He said that had been the practice in the coal industry for many years. 52 He also identified observation-type methods as looking for "imperfections in the conglomerate, joints, cracks, et cetera, and when they were drilling roof bolt holes, they would also be able to gain some impression as to what the state of the conglomerate might be according to whether the drill steel moves through continuously, or whether it was jumping or whether it got jammed. So they are not direct measurements of the stability of the roof, but they are observations and measurements that can be used to make a judgment as to the possible stability of the roof". 53 He was not aware of any other method of assessing the soundness of conglomerate roof as at July 1998. He had been involved in a project in relation to the use of Acoustic Energy Meters, which is designed to make the roof testing method quantitative as opposed to qualitative. That project commenced in 2001. The equipment has not yet been used within the "hazardous zone", that is within 100 metres of the working face because of the electrical nature of the equipment. He noted that the equipment is not a replacement for, but an aid to, the human ear. He said: "We have found that 90 per cent of the time the result of human ear and the meter comes up with the same, the same outcome. It's only on a small percentage of cases that there is a difference in interpretation. So it doesn't replace the human ear. It's basically aids the human ear in the mine." (sic) 54 An opinion of Darryl Kingston Stevenson was tendered in evidence by the prosecutor and he gave oral evidence in relation to it. Mr Stevenson is a Geologist with his own company, Geological and Mining Services Australia Pty Ltd. He is the senior Geologist at Leigh Creek Coal Mine in South Australia. It will be recalled that Dr Frith recommended in his conclusions that an opinion ought be obtained from an expert Structural Geologist. Mr Stevenson's opinion, as I understand it, fulfils that objective, and was prepared without his having inspected the mine and the site of the accident. Mr Stevenson's conclusions were as follows: On Monday 6 July 1998 a major roof fall occurred in B Heading near the proposed No. 3 Cut-Through in a section known as the Sump Headings. A section of the immediate roof detached from the overlying strata killing one miner and injuring a second. Several people leading up to and following the major roof fall that killed the miner made a number of observations that have enabled this Author to postulate on the causes of the roof failure: Northeast to southwest trending faults were observed and mapped within several roadways and were expected to be intersected within B Heading. The easternmost fault was intersected during the early hours of 6 July 1998, mining within B Heading ceased, and roof support operations were commenced. The special care required when mining in a direction sub-parallel to fault strike was acknowledged by Mr R Wallace, an experienced miner. Within the unsupported and newly supported section of B Heading a number of other geological features were present and observations noted. The overall impression was that of an area of the mine that was not considered to be "normal." Water was observed dripping from the roof, and guttering, rib spalling and weighting on brattice props was also observed. A noticeable roof separation/parting had formed and was detected by the miners involved in roof bolting and there was also a "sedimentary structure" which appeared to delineate the deteriorated area. Prior to the fatal fall, roof deterioration and falls were observed to commence at the face, near the newly intersected fault, and proceed outbye. The last major fall prior to the fatal fall terminated about 2 m inbye the last line of installed roof bolts and resulted in what is described as an approximately 2 m wide lip of unsupported roof. This remaining 2 m wide lip failed during an attempt to remove the drill steel from the final test hole. Studies completed after the accident have identified that the fault, "sedimentary structure", floor and roof joints, fractures within the Great Northern seam and B Heading are aligned sub-parallel to the Principal Horizontal stress Direction. This alignment is likely to have contributed to the "opening up" of the strata, allowing water to enter the area and generally reducing the strength of the immediate roof. The alignment of these features with B Heading is likely to have reduced the ability of the immediate roof to "beam" across the roadway. Studies have also identified a slickensided sub-vertical surface within the "sedimentary structure", a clay-like matrix within parts of the conglomerate and alteration minerals on joint and parting surfaces. This author believes that a sub-horizontal parting/zone of weakness was present within the immediate roof at about 400 to 450mm into the strata within B heading inbye of No. 2 Cut-Through. The interaction of the Principal Horizontal and mining induced stresses acted to "open up" the strata, reducing the friction between structure boundaries and allowing water to enter the sub-horizontal parting and further weaken cohesion within the immediate roof through the alteration of minerals within the conglomerates matrix and cement. Removal of the underlying coal, jolting from the continuous miner picks and vibrations from the Falcon roofbolter further weakened the roof strata. Roof failure commenced at the interface of the roof material with the fault. This initial fall further reduced the confinement of the strata below the parting. Under gravitational forces and with movement weakly restricted by the reduced friction between joints and the slickensided "sedimentary structure" roof failure proceeded to the last line of installed roof bolts. The most obvious warning signs of the impending accident were the rapid roof deterioration and failure that commenced soon after the fault was intersected, the outbye progression and morphology of the falls, and the presence of a roof parting in the immediate roof. 55 Mr Stevenson in cross-examination described the parting or weakness in the conglomerate layers, which related to the fall, as being unobservable before the fall because it was within the conglomerate body itself. He agreed that the loading evident to Dr Frith on the wooden props outbye the line of fall may or may not have been evident prior to the fall. Floor heave was also a possibility which would have imposed pressure on the props, although he thought it more likely the loading was from the roof. On the evidence he could not tell. 56 Mr Stevenson described the percussive effect of the continuous miner striking the conglomerate although that was a normal experience in the mine. In the context of discussing the roof fall, he expressed the view that the vibration set off by the roof bolter could have an effect but he could not be certain. He also accepted that percussive drills do not themselves cause the roof to fall. 57 Mark Levey, the Mine Manager at Wallarah at the time of the accident, was called in the prosecution's case. Mr Levey had extensive experience in various positions in the coal mining industry with a degree in Mining Engineering. Mr Levey had signed off on the minimum support rules applicable at Wallarah in relation to extraction mining. He testified that no other written instructions were provided to mining crew members in relation to support and there was no reassessment undertaken of roof structures. No general oral instructions were given with respect to the erection of roof support or the assessment of roof stability. 58 He said that the practice with respect to the erection of roof support was that when conditions were good the minimum support rules would suffice, and with bad roof, temporary support (timber props) was to be installed prior to the installation of permanent support (bolts primarily). He was definite about this practice, of which he was aware from his role as Under Manager at the mine for three years between 1998 and 2002. This was not a reference to brattice props. 59 He recalled two occasions in the first half of 1998 when temporary timber supports were utilised. He said ". . . we had trouble getting the hand held Falcon bolter in to bolt the roof up because there was so many props". In examination in chief he said this: Q. Is it the usual practice to set temporary support in the vicinity of drill holes before commencing drilling a hole? A. In good conditions? Q. In any conditions? A. It depends. Q. It depends, does it? A. If you have got good roof conditions it depends how far you move forward before you have begun your bolting process. But it wouldn't be the normal situation to put in temporary support in good roofing condition whilst installing a bolt. Q. Were there any occasions when you witnessed bad roof conditions where this did not occur? A. No. 60 He testified that timber props were the only temporary support available in Panel 3 on 6 July 1998. In other panels props were available and in panels "up north" both panels had continuous miners with rig-mounted drills on them which provided temporary support. 61 In comparing the use of rig-mounted roof bolters and Falcon bolters Mr Levey was asked in chief: Q. Which was the safer method? A. Both systems are safe. Q. How is the hand held Falcon method safe? A. In good roof conditions they are both the same. In poor roof conditions, one, you carry out the temporary support manually, the other is done hydraulically. They are both safe. Q. If you carry out the temporary support with a hand held method is that the case? A. Yes. Q. You are talking about timber props there? A. Yes. Q. Putting timber props in as temporary supports do you have to go under unsupported roof? A. No. Q. How is that to be avoided? A. Well, as you advance into poor roof you install a prop in advance as you move forwards but no more than 600 to 700mm, such you are always working in the influence of the previous support, you always have another support beside you. . . . . A. If you have got two metres of bad roof you will put up a row of timber across so high, put up the timber unsupported by the timber you previously set until you get where you want to support it permanently, bringing in the Falcon bolter to put up all the required permanent supports in between the timber, the bolts go up between the timber then you remove that temporary support. 62 He also gave the following answer in response to a question in chief: Q. What instruction, if any, did you provide to undermanagers or deputies in relation to assessing the requirement for extra support in conditions other than normal? A. That it be supported adequately for the level of deterioration of the roof. 63 Mr Levey described in cross-examination why rig-mounted bolting equipment was not being used in the area of the accident as being the result of the conditions met. He said: "A. . . . . the height of our workings was such that it was impractical to use the rigs". . . . . A. . . . . the overall seam thickness decreased in that area of the mine. Now, you have got to leave coal on the floor to give us a cover above an extremely weak clay stone floor that is below that, so you need half a metre of coal above the clay to ensure that you can continue to move forward, otherwise you bog your equipment. When you take that into account, there was no height left to practically use the rigs. . . . . Q. What happened when the rigs were damaged because of the heights at which they were working? A. They were damaged in many ways, but a general one would be they have bumped the drill mast and that has leaned forward or lent backwards, and because of the clearances they would bump up against it with the roof. This machine is 60 tonnes, it doesn't worry too much about that sort of thing, so, if it wants to drive forward it will damage the drill mast. It is a metal rod that sits up beside the part of the drill rig and it gets bent. Now, you can't use it then because the drillhead that slides up and down the drill mast doesn't function any more, it is on a bent piece of metal, so you have to take it off 64 An Inspector of Coal Mines of 18.5 years experience, Anthony Arthur Ryan, investigated the accident. He first arrived at the mine at 6.30am on the date of the accident and arrived at the underground site at 10.00am. He later inspected the accident site twice, one in company of Professor Moelle, and once with Dr Frith. Inspector Ryan described the scene consistently with the descriptions given by others who were present on the day. His description was: When I arrived in that general area, my first observations were it was fairly damp, the intersection on the out-bye side of that accident site, was probably about 20 metres out, it had water in it which was part way up my knee length boots, and the group with me walked in and had a look at the general area. There were work men in the vicinity where there were pieces of falling stone. I could see a number of timber props set around the area. I think from memory there were some roof bolts drilling steels over on the left side as we approached the area, hoses running up towards the fall, which I assumed were air or water hoses, because they are consistent when you're using roof bolting equipment, or even in the mining operation. There was ventilation brattice affixed to props on the right hand side of the roadway, several large pieces of stone which I saw on the floor and the top end of a roof bolting machine I assumed at the time to be a Falcon roof bolter, which was protruding from underneath one of the pieces of stone, water dripping from the roof from several of the holes which had been previously drilled, and a geological disturbance from memory running across the roof of that roadway at an angle of probably 45 degrees from memory. There appeared to be an area of collapsed roof on the in-bye side of where these props had been set. And going back a step, before I got to the intersection, I referred to the out-bye, I could see continuous mining (sic - the continuous miner) over on the adjacent roadway. 65 The first issue to which I turn is the submission made by the defendant that was said to answer the prosecutor's case concerning the exposure to risk when Messrs Dickson and Carroll worked under unsupported roof. As I apprehend it, the defence, if good, would run in the context of the charges in both matters. Section 33(2) of the 1983 OHS Act (the Act under which the charges are brought) provides: A person is not guilty of an offence under Part 3 in respect of any act or omission which is expressly required or permitted to be done or omitted by or under the associated occupational health and safety legislation. 66 Section 39 of the 1983 OHS Act provides: The provisions of the Mines Inspections Act 1901, the Mines Rescue Act 1994 and the Coal Mines Regulation Act 1982 and the regulations and rules made thereunder shall, for the purposes of this Act, be associated occupational health and safety legislation. 67 Section 174 of the CMR Act enables the making of regulations not inconsistent with the CMR Act and, in particular, with respect to "the support of the roof and sides of working places and roadways in mines and the withdrawal of that support". The Coal Mines Regulation (Support - Underground Mines) Regulation 1984 is a regulation made pursuant to that power. 68 Section 102 of the CMR Act requires each coal mine to have support rules for underground mines. Those support rules will meet the requirements of the CMR Act only if they are sent to the District Inspector (s105) and the District Inspector has served a notice confirming the rules on the manager of the mine (s105(2)). The support rules take effect seven days after the date of service of a notice of confirmation by the District Inspector (s110) and the support rules must be complied with by all persons employed at the mine (s112). 69 The minimum support rules required for a remote control miner (see par. [21] of this judgment) are rules conforming to those provisions, and rule 3 provides that workmen are not to proceed beyond the last test hole or temporary support unless the roof has been tested by sounding with a metal bar or suitable metal object & found secure. 70 Upon the basis of these statutory provisions and the minimum support rules, it was submitted that workmen are expressly permitted to proceed beyond the last test hole or temporary support in the circumstance described in rule 3. In the present matter the roof was tested by sounding with a metal bar and determined to be secure. It was submitted that it follows where any of the workmen had proceeded beyond the last test hole or temporary support, they were expressly permitted to do so under associated occupational health and safety legislation. Thus, no finding of guilt could be entered in these matters as a consequence of the operation of s33 of the 1983 OHS Act. 71 The prosecutor's position was that s33(2) of the 1983 OHS Act provides no answer to the charges. 72 It was accepted by the prosecutor that the minimum support rules were made pursuant to s102 of the CMR Act and that the CMR Act is associated occupational health and safety legislation for the purposes of s33(2) of the 1983 OHS Act. It was submitted that the charges relate to the omission of the defendant in its "failure to provide or maintain systems of work that were safe and without risks to health". Those omissions are not omissions which are expressly permitted by the support rules as contended for by the defendant. Nothing in the support rules expressly permits the defendant to fail to provide or maintain adequate systems of work in relation to either the erection of roof support or the assessment of the stability of roof structures. 73 It was submitted: (4) It may be argued that the support rules permitted employees at the mine to perform the actions that were performed at the time of the alleged offence. However, that is an entirely different matter to the support rules permitting the defendant to fail to provide or maintain adequate systems of work. (5) In any event, the support rules in question were minimum support rules. As such they do not expressly permit any act or omission but merely prescribe minimum standards below which the persons to whom they are applicable must not fall. (6) In the alternative, to the extent that the support rules deal with the assessment of the stability of roof structures they are not rules for or with respect to the support of the roof that are enabled by the legislation - s174(2) Coal Mines Regulations Act 1982 (NSW). In these circumstances the support rules would not in any event preclude the charge in IRC6727 of 2001. 74 The minimum support rules, as has been earlier noted, are rules adopted and approved in accordance with the Coal Mines Regulation (Support - Underground Mines) Regulation 1984. Regulation 6 imposes a burden on the person for the time being in charge of a part of a mine to "ensure that the roof and sides of every travelling roadway and working place in that part of the mine are secure in accordance with the support rules for that mine". Apart from the duty, two things seem to me to emerge relevantly from that regulation. The first is that the duty is to be carried out in accordance with the support rules and the second is that the roof is to be "secure" in accordance with those rules. 75 In the present case, the adopted rules are referred to as "minimum" support rules. The qualification effected by the use of the word "minimum" seems to me to have two possible meanings: either that the rules provide the minimum means of securing the mine roof at any point, regardless of conditions, or that they constitute the minimum for optimum conditions and that something greater than the minimum must be applied as conditions deteriorate. 76 On the first view, there is an overwhelming force in the argument advanced for the defendant that Messrs Dickson and Carroll were working where the minimum support rules permitted them to work at the time of the roof fall. 77 If the rule is to be interpreted in this way, it seems to me that the defendant has made out a defence under s33(2) of the 1983 OHS Act in that the act of performing the work was expressly permitted to be done under the CMR Act, Regulations and Rules, they being associated occupational health and safety legislation. 78 On the other hand, if the second approach to the rules were taken, two problems arise. The first is that it is difficult to see how the rules would conform with regulation 6 as being support rules which require the relevant person to ensure the roof is secure in accordance with them. That is, the uncertainty resulting from an absence of precise direction would seem to minimise their efficacy. Yet, there is no contest that the rules were approved as being in conformity with the regulations. 79 The second problem which emerges is the effect and consequence of a rule which prescribes minima but not maxima. 80 Such a rule could only operate, and be intended to operate, on the basis that the minimum standard adopted by those rules for supporting the roof would be applied and a discretion would be extended to relevant individuals to determine what was appropriate in the light of conditions then faced. That discretion, in the context of the mining experience, could only be exercised by persons having a knowledge and experience which would enable them to make a reasoned judgment having regard to their observations. Such an approach could not preclude the possibility of error, given that the indicia of poor roof do not identify the necessarily appropriate response. Providing that the minimum support rules were not observed blindly, that is, without regard for deteriorating conditions, it would seem that any value judgment taken by those on site at the time, at least if undertaken bona fide, might satisfy the injunction to ensure the roof was secure even though the roof might not in fact be secure. 81 The reason, in my view, for such a conclusion is simply that the individual/s concerned would have taken what were perceived to be appropriate steps to ensure the roof was secure. They would have been dealing with imponderables, such as an unobservable horizontal parting in the conglomerate layer as here, and thus would not have failed in any relevant sense to act in conformity with the rules. 82 If the intention of the minimum support rules were to be that the only acts which could conform with the obligation to ensure security of the roof are those which actually achieve security of the roof, then the rules would be imposing an impossible burden on the decision maker. I prefer the view that the minimum support rules, constructed as minima, recognised the virtual impossibility of prescribing a reasonable standard to meet all circumstances in the mine. If it was thought that any risk must be met by the minimum support rules, the departmental approval should not be forthcoming for rules which prescribe minima. This was not the case. 83 If it was not intended that the minimum support rules provide a discretion of the kind to which I have referred, it would have been very easy to prescribe the minimum support rules as they now stand as applicable in good conditions and a quite different approach to deteriorating or poor conditions. If, as seems to have been suggested in the prosecution's case, the method of timbering before rock bolting was necessary to be employed (this method was outlined by Mr Levey and referred to by Mr Pezely), that minimum standard in poor conditions could have been adopted. However, it was not. This was not a case where the crew were blindly applying the minimum support pattern provided in the minimum support rules. They were adopting, as a result of the consultation between Messrs Wallace and Tytherleigh, a closer bolting pattern which was thought to be an appropriate reaction to the changing circumstances. I find, on the evidence, that the mining crew did undertake a changed form of securing the roof in response to the conditions they were facing and that on this alternative interpretation of the minimum support rules, they were acting in conformity therewith. Accordingly, a good defence is made out under s33(2) of the 1983 OHS Act on this ground also. 84 I am unable to accept the prosecutor's argument that a distinction is to be drawn between the support rules and the obligation of the defendant to provide or maintain systems of work that are safe and without risks to health. In my view the support rules were directed to precisely that objective. They are concerned to ensure the roof is supported to avoid its falling on a workplace or driveway. In the context of underground mining, it is difficult to perceive any necessary function more important to the safety of workers in the mine than the support of the roof. 85 Further, it seems to me that supporting the roof is a process which has two elements: the assessment of the stability of the roof and the response to that assessment in the nature of the support to be provided. While supporting the roof embraces assessment of the roof stability, I do not consider that assessment of the roof stability encompasses the actual support of the roof. This natural dichotomy was evident also in the questions of senior counsel for the prosecutor to Mr Levey. In any event, if the particulars were ambiguous, which I do not consider they are, I would read them down in the defendant's favour. 86 In my view, assessing can only relate to the testing of the roof for stability. The phrase "in relation to" while wide is not unrestricted and cannot extend the meaning of the phrase into an area unrelated to assessing. It is conceivable that it might include the erection of support necessary to enable an assessment to be done but it could not include the erection of support subsequent to the assessment of the condition of the roof. While the prosecutor submitted it would be "absurd" to read down the meaning of "assessing" in this way, that is, in my view, not so. It is merely to give the words chosen by the prosecutor their natural meaning. 87 These views mean that the defendant has made out in all relevant respects a defence under s33(2) of the 1983 OHS Act. In coming to these views, I have taken into consideration the observations of Haylen J in Rodney Morrison v Tahmoor Coal Pty Limited [2001] NSWIRComm 327, 3 December 2002 (unreported). In that matter, in complicated circumstances which do not require repetition here, an employee was found drowned in a body of water underground adjacent to a point at which he was working. An employee with whom the deceased was working had been sent away a short distance and only briefly. In discussing the proposition that the close presence of another person when work was being performed was an obvious and effective method of work, Haylen J said: It was common ground, however, that the Coal Mines Regulation permitted an adequately trained employee to work unaccompanied underground. Mr Hill was authorised under this regulation to work alone. I accept the defendant's submission that the operation of s 33 and s 39 of the Occupational Health and Safety Act 1983 had the effect of rendering a person not guilty of an offence under Part 3 in respect of any act or omission which is expressly permitted to be done under associated legislation (here the Coal Mines Regulation Act 1982 and the Regulation). In addition, the defendant correctly pointed out that there was no attack on the issuing of this authority to Mr Hill, either because the Mine Manager could not have reached the requisite level of satisfaction and/or because Mr Hill was not appropriately trained. This simple and effective solution is therefore of no moment in the present proceedings. 88 However, I intend to examine the question of an offence arising under s15(1) of that Act in the alternative, assuming the views I have formed in relation to the defences are not correct. It is apparent that the techniques used by miners and their supervisors for assessing the stability of a roof involve principally the senses and are even perhaps antiquated. The sounding of a conglomerate roof with a steel; the observation of a roof which might show water, slurry or stone and coal falling from it; listening for sounds indicative of a weaker roof or problems in the roof, all involve an individual's assessment by what seems to be an instinctive or learned reaction closely concerned with self-preservation. The evidence shows that the testing process is undertaken by all miners in a team on a continual basis. The environment in which the work is undertaken is obviously one involving inherent dangers, the avoidance of which depends much upon the reaction of the persons involved to the changing conditions they face. There appears to be, on the evidence, no process or procedure available which would produce for miners information certain as to the condition of a roof under which they work. Indeed, the very act of roof bolting, which is designed to "pin" the immediate strata of the roof to some strata above it seems to me to be dependent, for its effectiveness, upon strata conditions which may or may not exist, unbeknown to the miners. Yet, a roof bolted in an acceptable pattern and by an acceptable method is recognised within the industry as one under which it is "safe" to work. 89 Here, the work of roof bolting itself was being undertaken to secure the roof in this way but the roof fall occurred in circumstances where the mining crew were not able to anticipate the fall by the application of these standard testing procedures. There was no other means available for discovering its weakness. 90 One issue at the heart of the prosecution is whether the bolting process, undertaken with a Falcon roof bolter which itself provided no roof support, involved a failure by the defendant/s of a kind relevant to create the offence/s raised in the charges. 91 The prosecution alleges that the failure to utilise rig-mounted bolting machines of the type which were used in other parts of the mine is the relevant failure. The defendants argue that the rig-mounted equipment was unsuitable for use in this area because of the limited space between the floor and the roof and that after the cessation of mining, following the accident, special equipment had to be designed and constructed to enable the continuation of mining in this area. 92 It is evident that the opinions of the three experts in relation to this accident are responsive to the circumstances which developed, rather than critical of the process which was being undertaken prior to the accident. The opinions necessarily look at probabilities and, as Dr Moelle observed "bolting operations under erosional Teralba conglomerate are evidently best conducted with bolting machinery that allows the operator to be under supported roof at any time" (my emphasis). This observation shows the response to the circumstances of the accident rather than an anticipation of what would have, or should have, happened in terms of work practices prior to the accident. 93 These aspects of the experts report go directly to the foreseeability of the accident and the question of whether there was any relevant, and identifiable, failure by the defendant/s. 94 Mr Stevenson's conclusion that the final roof fall occurred when Mr Carroll was attempting to remove the drill steel from the roof, a fact supported by those present including Mr Dickson, indicates that while the parting in the roof was evident to a degree from the jamming of the drill steel and the evidence which had come from the hole during drilling, including the water, none of the very experienced miners present at the time, and observing these features, recognised them as notifying the actual danger which was present. Mr Carroll's attempt to remove the steel is not evidence of a wilful disregard for the apparent danger but rather indicative of an absence of recognition of a hidden risk by persons experienced in these circumstances. There is no evidence from which it can be gleaned that any person then present, not having available some expert opinion on the matter in the light of the accident, would have formed the view at the time that the undertaking was seriously dangerous. In other words, it cannot be concluded that an assessment of the roof at the time would have produced the view that Mr Carroll was at serious risk in undertaking the task he did. Where then is the employer's failure? 95 This was not a case of an employer delegating responsibility for safety to another. The employer had prepared the minimum support rules and obtained the departmental approval for them as apt in the circumstances of the mine. 96 In any event, had the roof been supported with timber props in advance of the area in which Messrs Dickson and Carroll were bolting, then necessarily, any worker who might have installed the timber props, a process involving measurement, cutting of the prop to approximate size and then hammering wedges beneath it so as to create a tight fit, would then have been working, to an unavoidable extent, under unsupported roof. 97 As to the prosecutor's submissions regarding the use of rig-mounted bolters, I am not satisfied beyond reasonable doubt that the conditions of the mine permitted their use in the area of the fall. Mr Levey's evidence in that regard, I consider, is sufficient to raise a reasonable doubt on that matter. His evidence also was that rig-mounted bolters are not always used in other parts of the mine although in most panels Falcon and rig-mounted bolters were used as a routine practice. 98 The concept of ensuring safety under the provisions of the 1983 OHS Act has been long recognised as requiring the demonstration that a defendant has failed by act or omission in a way which is causally connected with the resulting risk to safety. Given the circumstances to which I have referred and the necessity of the relevant parties to respond to their assessment of roof condition, I find that the prosecution has not established a relevant failure by the defendant in relation to s15(1) of the 1983 OHS Act. 99 I find the defendant not guilty of the charges in these matters, which I dismiss. I reserve the question of costs. 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.