| JURISDICTION : DISTRICT COURT OF WESTERN AUSTRALIA LOCATION : PERTH CITATION : THE MINISTER FOR HEALTH -v- BRAMBLES AUSTRALIA LTD [2009] WADC 111 CORAM : O'NEAL DCJ HEARD : 18-22 MAY 2009 DELIVERED : 31 JULY 2009 FILE NO/S : CIV 1086 of 2008 BETWEEN : THE MINISTER FOR HEALTH Plaintiff
AND
BRAMBLES AUSTRALIA LTD
Defendant
Catchwords: Contract - Construction of term - Performance and breach - Damages - Remoteness - Negligence - Duty of care - Standard of care - Breach of duty - Statutes - Statutory powers and duties - Construction
Limitation of actions - Contract - When time begins to run Legislation: Hospitals and Health Services Act 1927 s 15, s 15(2), s 7(1), s 7(2)
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Result: Judgment for the plaintiff Representation: Counsel:
Plaintiff : Mr P G McGowan
Defendant : Mr J R Criddle
Solicitors:
Plaintiff : Talbot Olivier
Defendant : SRB Legal
Case(s) referred to in judgment(s):
Commissioner of Taxation (Cth) v Everett (1980) 143 CLR 440
Hadley v Baxendale (1854) Exch 341; 156 ER 145
Hillstead v The Queen [2005] WASCA 116
Nelson v John Lysaght (Aust) Ltd (1974) 132 CLR 201
Toll (FGCT) Pty Ltd v Alphapharm Pty Ltd [2004] HCA 52; (2004) 219 CLR 165
Wyong Shire Council v Shirt (1980) 146 CLR 40
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Introduction 1 In 1996 an employee of the Bentley Hospital was injured as she opened a large industrial waste bin. The bin was the property of the defendant, trading under the business name "Cleanaway". I will use that name to refer to the defendant in these reasons. The bin had been provided to the hospital pursuant to the terms of a contract awarded by the plaintiff to Cleanaway in December 1995 (the "Contract"). 2 The employee's name was Kerry Muir. Ms Muir was employed as an orderly at the hospital. The injury that she received was to the rotator cuff of her shoulder and it was significant and disabling. As a result of her accident she received Workers Compensation payments totalling about $92,000, together with various statutory allowances provided for under the Workers Compensation and Rehabilitation Act 1981. In August 1999 however she commenced an action against her then employer the Metropolitan Health Service Board ("MHSB"). As will be seen the MHSB was, at that time, responsible for the administration of Bentley Hospital. By the statement of claim filed in that action she alleged that the MHSB, as her employer, had breached a duty of care owed to Ms Muir as an employee of the Bentley Hospital. The various acts of negligence alleged against the MHSB were said to have caused Ms Muir's injury. 3 On 26 October 2000, a settlement was reached with respect to Ms Muir's action. The MHSB consented to judgment in the sum of $140,000 "exclusive of payments and allowances made pursuant to the Workers Compensation and Rehabilitation Act and costs fixed at $15,700 inclusive of disbursements". In this action the plaintiff seeks to recover the money paid to Ms Muir on account of her injury, other than the amounts paid as costs and disbursements. 4 For the purposes of this introduction I will refer, in broad terms, to the issues raised on the pleadings. 5 The plaintiff sues for what is alleged to be either a breach of the Contract or negligent failure to take care for the safety of employees at the Bentley Hospital. The plaintiff seeks either damages for breach of Contract, an indemnity under the terms of the Contract or contribution and indemnity pursuant to the provisions of the Law Reform (Contributory Negligence and Tortfeasors' Contribution) Act 1947 (WA) (The "Contributory Negligence Act"). (Page 4)
6 Cleanaway denies responsibility for Ms Muir's injuries. It also denies that it breached any duty owed either to the plaintiff or to Ms Muir and puts the plaintiff to proof that it was in fact any breach of duty by the defendant that caused Ms Muir's injury. 7 Cleanaway also raises several defences at law. First it is said that, whatever happened to Ms Muir, the plaintiff has not suffered any loss. The MHSB and the plaintiff, the defendant says, are in law different persons. Any loss suffered was suffered by the MHSB as it was the MHSB that made the payments to Ms Muir. Similarly Cleanaway says the plaintiff was not Ms Muir's employer at the time of her injury, could not have been negligent in respect of Ms Muir's accident, and therefore was not a tortfeasor within the meaning of s 7(1)(c) of the Contributory Negligence Act. And, Cleanaway says, with respect to any claim in contract other than the claim for indemnity, any such claim is statute barred because it arose more than six years before this action was brought. Any cause of action in contract, it says, arose as soon as bins were delivered to the Bentley Hospital. 8 Finally, Cleanaway argues that on its proper construction, the indemnity in the Contract does not require it to indemnify the plaintiff for any loss or damage arising out of the defendant's performance of the Contract where there has been negligence on the part of the plaintiff or its successor the MHSB. Cleanaway alleges that the MHSB's negligence did cause or contribute to Ms Muir's injury. Cleanaway alternatively seeks apportionment of any contribution or indemnity on the basis of that alleged negligence. An allegation of contributory negligence against Ms Muir was abandoned at trial.
Background 9 In 1994 Bentley Hospital was a large established public hospital. It had general, geriatric and mental health wards among its various facilities. The hospital site covered and covers a large area of land on both sides of Mill Street. 10 As might be expected the waste generated by the hospital was and is considerable. 11 Ms Kerry Muir was born in 1950. She was first employed at the Bentley Hospital in 1992 as a casual cleaner and orderly. Her day to day duties included cleaning offices, emptying paper bins, vacuuming and mopping floors and gathering up trash and bagging it. After waste was bagged, cleaners like Ms Muir would put it in a trolley and wheel it out to (Page 5)
bins where it would be disposed of for collection. The bins in which she placed the trash were "dumpster" type bins. 12 "Dumpster" bins are a common feature of the modern landscape. Anyone who has peered down a back alley in a city or looked behind any commercial or industrial premises would recognise dumpster bins immediately. 13 In 1995 the defendant trading under the name "Cleanaway" was Australia's largest and, according to its own promotional literature, most respected waste management company. The defendant's Cleanaway business operated in the United Kingdom, Europe, the USA and Asia as well as Australia. Its head office was in Sydney but its regional office for South Australia and Western Australia was in Perth. It employed 192 people in Western Australia at 6 different sites. In 1995 it had been trading since at least 1979: Exhibit 13. 14 Grahame Pratt gave evidence for Cleanaway. Between 1995 and 2000 he was the sales manager for Cleanaway with a team of five sales people beneath him. One of the members of his sales team was Ashley Dixon. Mr Dixon also gave evidence for Cleanaway in a deposition made pursuant to O 38 r 11 of the Supreme Court Rules 1971. I was provided with a transcript of that evidence. 15 Mr Pratt described the change that occurred with respect to the management of waste in hospitals commencing in about 1995. Prior to that time hospitals were allowed to incinerate their own waste. Greater environmental consciousness ended the practice but resulted in hospital waste being directed to landfills. Concern with that practice then led to the adoption of a measure of waste recycling. In 1995 when Mr Pratt joined Cleanaway, Cleanaway was providing some waste recycling services to the Bentley Hospital. Although questions in cross-examination by counsel for Cleanaway suggested that the City of Canning was then providing general waste collection from the hospital's dumpster bins, Mr Dixon suggested that waste services were provided at that time by an American company called Browning-Ferris Industries. 16 In early 1995 discussions began between administrators at the Bentley Hospital and representatives of Cleanaway for the coordination of the hospital's waste disposal requirements. They discussed the prospect of Cleanaway providing all of the hospital's waste collection services ranging from the collection and disposal of clinical waste, liquid waste, recycling and general waste. Eventually the hospital administration took the (Page 6)
proposal to the Western Australia Government Health Supply Council. The chairman of the Council was a delegate of the plaintiff.
The Contract 17 By request for tender number HSC562/95 tenders were sought by the plaintiff's delegate for the provision of waste removal services to the Bentley Health Service: Exhibit 10. The closing date for tenders was 27 October 1995. The terms of the request required tenderers to address its terms and provided, at s 3, a number of conditions that would apply to any agreement reached as a result of the tendering process. 18 At cl 2.7, dealing with one of the conditions of tendering, the request provided as follows under the heading "Alternative tenders": "Tenderers shall submit full details of all deviations from the requirements of this tender on a clause by clause basis." 19 At cl 3.8.1, the Request provides: "The Contractor acknowledges that Bentley Health Service is relying on the professional skills and judgment of the Contractor in the performance of the contract." 20 Clause 3.17 headed "waste bins" provides details of the specifications for the bins the subject of the request. This provision (erroneously numbered 3.18.1 in the document) needs to be set out in full: "The contractor shall supply all waste bins required … and maintain all bins to a safe and operational standard. All bins are to removed, cleaned and disinfected at least three (3) times per year as directed by the contract manager. • Bins provided are to be 240 litre, 3 cubic metre and 4.4 cubic metre. • All bins (where applicable) are to have the stopper/plug securely in place at all times. • Bin lids may be either plastic or roll top design or an approved modification. • The force required to open or close the container lid shall not exceed 100 Newtons push/pull or 40 Newtons lift. (Page 7)
• Repairs and maintenance of containers, including fire damage, will be the responsibility of the contractor." 21 The 3 and 4.4 cubic metre bins are dumpster bins of the kind that I have described. The 240 litre bins are the large two wheeled plastic bins that are commonly used for household trash. It is only the 3 cubic metre dumpster bins that I am concerned with in these reasons. 22 The General Conditions of Contract for the Supply of Services ("General Conditions") prepared by the State Supply Commission (Exhibit 9), are expressly incorporated by reference into any contract made as a result of the tendering process by cl 3.1.1. 23 From the evidence of Mr Pratt it seems that in 1995 Cleanaway had been looking at alternate designs for the lids of its bins. At about the same time Cleanaway was having discussions with the Bentley Hospital administration testing was done of plastic bin lids in place of the conventional steel lids. As Mr Pratt said in his evidence, the specification of "either plastic or roll top design" for lids in the request for tender at cl 3.17 was incorporated as a result of the discussions that had taken place between the defendant and those involved in arranging the request for tender. It did not appear however that Mr Pratt had a good grasp of technical specifications or details of Cleanaway's bins. In particular, if his evidence is accepted at face value, he did not understand the implications of the specification with respect to force "100 Newtons push/pull or 40 Newtons lift". 24 On 27 October 1995 Cleanaway submitted its tender in response to the plaintiff's request: Exhibits 12 and 13. Under the heading "Occupational Health & Safety", Cleanaway responded to one aspect of the request for tender as follows: (Page 8)
25 The designation "N" is of course an abbreviation for Newton, a measure of force. In these reasons I will refer to the two paragraphs set out above as the "OH & S term". I will refer to the last sentence of the OH & S term as the "69N stipulation". 26 The tender includes a summary of the waste system to be supplied and the proposed cost. The summary lists "two 3 m3 front lift bins" for general waste. 27 Clause 2.1 of the General Conditions requires that "all Services rendered shall conform to the Specification and the standards specified in the Contract". "Specification" is defined in the General Conditions as: "… any Special Conditions, Technical Specifications and Schedules forming part of the Contract; and such Specification shall be read with these General Conditions as an integral part of the Contract, but in the event of an inconsistency between the Specification and these General Conditions the former shall (unless the contract otherwise provides) prevail." 28 "The Contract" is defined within the General Conditions as: "… the document which constitutes or evidences or, as the case may be, all the documents which constitute or evidence the final and concluded agreement between the Commission and the Contractor." 29 There are two other provisions of the General Conditions which bear on the issues in this action. Clause 21 obliges the contractor to comply with all legislative and regulatory requirements that affect or apply to the services to be provided and says: "Without limiting in any way the generality of the forgoing, the Contractor shall duly and punctually observe, perform and comply with the provisions of the Occupational Health, Safety and Welfare Act 1984 and … codes of practice (if any) issued thereunder and having application to this Contract." 30 Under the heading of "Property Damage and Public Risk" cl 22 provides: "Subject to the next succeeding paragraph of this clause, the Contractor shall indemnify and keep indemnified the Commission and the Customer against all loss of or damage to (Page 9)
the property of the Commission or the Customer, and from and against any claim, demand, action, suit or proceeding that may be made or brought by any person against the Commission, the Customer or the employees, professional consultants or agents of the Commission or the Customer or any of them in respect of personal injury to or the death of any person whomsoever … arising out of or as a consequence of the supply or provision of these Services by the Contractor or his employees … and also from any costs and expense that may be incurred in connection with any such claim, demand, action, suit or proceeding. The Contractor shall not, under the last preceding paragraph of this clause, be rendered liable for or in respect of personal injury to … any person … resulting from any breach by the Commission of any provision of the Contract or any negligent act or omission of the Commission, the Customer or the employees, … or agents of the Commission or the customer or for or in respect of any claims, demands, actions, suits or proceedings, costs and expenses whatsoever in respect thereof or in relation thereto." 31 By a letter dated 19 December 1995 (Exhibit 70) the plaintiff's delegate Mr J Burns responded to the defendant's tender as follows: 32 In my view a reasonable person would have understood the Occupational Health and Safety term and in particular the first and last sentences thereof as a promise by Cleanaway intended to affect the legal relationship between it and the plaintiff if Cleanaway's tender was accepted. When the tender was accepted on 19 December 1995 the Occupational Health and Safety term, including the 69N stipulation, became a term of the Contract. (Page 10)
Cleanaway's Performance of the Contract 33 Following the acceptance of its tender Cleanaway engaged an ergonomist to evaluate the operation of the lids of their dumpster bins. I will refer to that evidence later in these reasons. 34 At the time Mr Dixon gave his evidence by way of deposition in May 2009 he had 20 years experience in the waste management industry. He commenced employment in 1992 as a territory manager within the metropolitan Perth area responsible for sales. He reported to Mr Pratt, the sales manager. 35 According to Mr Dixon at about the time of the tender discussions for the Bentley Hospital there had been a recognition by Cleanaway or its parent company that, with respect to the standard steel lids on front lift dumpsters, "there were issues with those lids". It was at that point, apparently as a result of some consideration by Mr Pratt and Cleanaway's workshop manager, that plastic bin lids were introduced. As best as I can determine, in about December 1995 or January 1996 a decision was made to phase out steel lids and replace them with plastic lids as new bins were ordered. 36 Still later in 1996 there was a further modification in the design of Cleanaway's bins. The height of the front of the bin was reduced and the rear of the bin increased so that the lid sloped forward rather than being flat. This design was described in the evidence as a "low profile" bin. 37 An issue of fact arises in this case as to what kind of bins were in fact supplied to Bentley Hospital and which type of bin was involved in Ms Muir's accident. 38 A series of office copies of "service contract forms" was tendered on behalf of Cleanaway: Exhibit 15, 16 and 17. These show that on 23 January 1996 Cleanaway initiated the internal procedure to have three dumpster bins placed at Bentley Hospital in connection with the Contract. Each form shows a start date of 5 February 1996. The customer name is in each case "Bentley Hospital". There are three different "site" names however: Mill St Centre, Bentley Lodge, and Bentley Hospital. In each case, at least initially, it was a three cubic metre bin that was specified. Ms Muir worked at the Mill Street Centre area of the hospital. 39 However with respect to the Bentley Hospital site, a "3" appears to have been crossed out and replaced with "4.5": Exhibit 17. That is, where the form first specified a three cubic metre bin it was amended to provide (Page 11)
for the larger bin. Subsequently, on 7 February 1996 a further "service contract form" bearing the same account number as the previous form for the "Bentley Hospital site" shows a request to increase the frequency of collection of waste from that bin: Exhibit 18. Then, on 19 February 1996 a further "service contract form" shows a request for a reduction in the size of the bin from 4.5 to 3 cubic metres: Exhibit 19. A handwritten comment on the form offers the apparent reason "insufficient room for truck to turn and put bin back in required location". 40 This last form, unlike any of the other such forms tendered into evidence, shows somewhat greater attention to detail in its completion. There is some justification for criticism that was made by counsel for the plaintiff of Cleanaway's recordkeeping. This form, unlike all the others, records the fact in the space provided that this bin is "owned by Cleanaway". It also records, by ticking the appropriate boxes, that wheels are to be included with this bin as well as a "D/Plug", that is, a drain plug. 41 Mr Dixon gave evidence that it was his standard practice with all large new accounts to attend site to inspect the bins within days after their delivery. His evidence was that the three cubic metre bins delivered to the Bentley Hospital were brand new, standard issue box bins, flat topped with plastic lids. 42 The bins provided by Cleanaway were typical "front lift" bins. As Mr Dixon said, trucks that are specially fitted with fork mechanisms empty these bins by driving the truck forward so that its forks engage sleeves on either side of the bin. The forks then lift the bin over the top of the truck, rotating it through 180 degrees. Gravity causes the bin lids to open and the contents of the bin are emptied into the truck. When the process is reversed the bin lids clang shut and are placed back on the ground. The truck then disengages and drives off. The system is one which allows the safe storage of large quantities of waste and their efficient collection. Quite obviously the bins have to be extremely robust to withstand repeated emptying.
The Accident 43 Kerry Muir gave evidence for the plaintiff. On 28 October 1996, Ms Muir began work at 6 am cleaning the clinic in "E block" of the Bentley Hospital. Depending on the roster, sometimes she was required to load rubbish into dumpster bins five times a week. The next week she wouldn't have to use the bins at all. On 28 October 1996, she loaded her trolley full of rubbish and took it out the back to the dumpster. (Page 12)
44 When Ms Muir was first transferred over to E and F block in about March 1994 her roster duties included loading rubbish into the dumpster. Her evidence was that when she first started doing that task in 1994 the dumpster bins had metal lids. She said that about eight months prior to her accident the bins changed in that the metal lids were replaced with plastic lids. Otherwise, the bins were about the same size. That is they were square and flat topped. 45 She said that on 28 October 1996 she started work at six in the morning. After she finished cleaning the clinic she loaded her trolley full of rubbish and took it to the dumpster. She stood at the front of the dumpster to start pushing the lid up and then walked around to the right side of the bin to lift it up. She pushed it with her left and right hand, in the same manner that she used whenever she had to open the bin. In order to get the lid to lock into place she had to push it up high enough so that it would "drop into a cog to keep it open". She was of course referring to the locking arm mechanism which can be seen in many of the photos that were tendered in evidence. She said that as she was "walking it up, walking around and lifting" she was "on my tippy toes at the end to push it back." In order to do that, whilst she was on her "tippy toes" she pushed with her left hand and then got under the lid with her right hand at the part of the edge of the lid that was closer to the hinges. She said that to get the lid into its locking position it was necessary for her to finally "jerk" the lid up with her right hand. 46 Ms Muir is 5 foot 5 inches (164 centimetres) tall and at the time of the accident weighed about 80 kilos. 47 In cross-examination Ms Muir readily accepted that the plastic bin lids were noticeably lighter then the metal lids. She was asked to agree that until her accident she didn't have any particular difficulty with the plastic lids. She said however that "they were always awkward". It was put to her that the plastic lids were much less awkward then the metal lidded bins. She said "not really". 48 Ms Muir said that as she jerked the lid upwards to try and lock it into position she felt a sharp pain in her shoulder. She kept working that day but the pain got worse. She reported the accident the next day and went to the doctors the day after that. While she later tried to return to work doing light duties she was unable to carry them out. She subsequently had an operation on her shoulder and has had various programs of physiotherapy and pain killing medication. (Page 13)
49 Ms Muir said that the bin was "probably about chest high" while she was standing facing it. Despite the awkwardness of the task of lifting the bin lid, Ms Muir said that she received no instruction from her employer as to how she should perform that task. I infer from this that the management of Bentley Hospital simply assumed that the task of opening bins was within the capacity of Ms Muir and other cleaners without any specific assessment of that task relying perhaps, from January 1996, on the Occupational Health and Safety term in the Contract. 50 Ms Muir appeared to me to be a sensible, straightforward and honest witness who gave her evidence without any embellishment. I accept her evidence as to the manner in which her accident occurred. 51 The issue of exactly what sort of bin and lid was involved in Ms Muir's accident involved a fair amount of time at trial. Mr Alan Wilkes gave evidence for the plaintiff. Mr Wilkes has worked at the Bentley Hospital since 1994. He was a gardener there between 1994 and 1999. He routinely used bins provided around the hospital to dispose of garden waste. 52 There was a storage area for the gardeners near the loading bay for F block. The storage area was about 15 or 20 metres from the dumpster bin where Ms Muir was injured. Mr Wilkes was in the loading bay at the time Ms Muir was injured. He heard her swear, looked, and saw that she was holding her shoulder. 53 Mr Wilkes was adamant that the bin involved in Ms Muir's accident was on casters and had steel lids. His recollection was that sometime after the accident the bins were changed to plastic lidded bins with a sloping front. That occurred, he thought, "probably a few months after" the accident. Mr Wilkes said that the first time he was asked to recall the circumstances of Ms Muir was "a couple of years later". The matter of what type of bins or lids were in use at the hospital was not something that was in the forefront of Mr Wilkes mind in October 1996. There is no reason to expect him to have a particular memory of that fact. The position is rather different for Ms Muir. 54 Mr Wilkes was a fit looking man who said that he was 5 foot 8 inches tall. He described his method of lifting the bin lids. He said that he would use a metal handle on the front of the bin lids and use that to throw the lid up until it caught in its first catch. Then he would walk around to the side of the bin and "walk the lid up until it got into the second catch". When the lids changed to plastic he said that it didn't make (Page 14)
any difference in the way he opened the lid. He would still "grab the side and throw it up. They were easier to throw up of course because they were plastic." 55 Jeffrey Reibel gave evidence for the plaintiff. He has been employed at Bentley Hospital since 1985. He has worked in a number of roles at the hospital. Between November 1994 and July 1996 he worked as an orderly in F block. His duties, like those of Ms Muir, included placing waste in the dumpster bin. Mr Reibel described them as 6 feet square and about 5 foot 4 inches in height. He said the bin had a split metal lid. He did not recall any change with respect to the types of dumpster bins being used in 1996. 56 Mr Reibel never used the bins again after July 1996 and was only asked to recall what types of bins were in use in 1996 in November 2008. The divergence between Mr Reibel's general description of the bin and the evidence of virtually every other witness, together with the amount of time that passed between Mr Reibel's use of the bins and his attempt to recollect what type of lids they then had makes it unlikely in my view that his memory can be trusted. 57 As a result of Ms Muir's accident there was an "incident investigation" and report prepared by some of the hospital staff responsible for occupational health and safety. This included Faye Sullivan and Annette Stewart. Ms Sullivan was a cleaner at the hospital between 1985 and 1999. She gave evidence for the plaintiff. Ms Sullivan's work did not require her to dispose of or deal with the rubbish or waste that was collected from the areas where she worked. In 1996 however she served as the staff representative on the hospital's Occupational Health and Safety Committee. Annette Stewart was the hospital's manual handling coordinator. The incident report prepared following Ms Muir's accident was tendered in evidence: Exhibit 49 and 49A. 58 The incident report describes three "contributing factors" two of which are relevant. The first "contributing factor" is described in this way: "Stood to one side using both hands – pushed lid but lid was heavy and didn't lift and slid back a bit." (Page 15)
59 The third contributing factor is described in this way: "Lid also was heavy and needed to click into place to be held up safely." 60 With respect to preventative actions the matter was apparently referred to Annette Stewart to consider and report back with solutions. A recommendation made by the Occupational Health and Safety Committee members, Faye Sullivan being one, was to provide a "step up block to reduce height comparative to bin. Requisition put into engineering." There was no admissible evidence as to whether this was in fact carried out, but on its face it would seem a simple and practical way to assist smaller members of the hospital's staff to be able to open the bin lids, subject to the assessment of that measure for any safety issues that it in turn might raise. 61 It is notable that Cleanaway tendered on the basis that it was going to provide plastic lids and none of the documentation following the accident suggests that did not occur. Given Ms Muir's accident, if there had been something as obvious as a failure to provide the plastic lids that had been promised, a complaint in that regard would be expected. To the contrary, it seems that the Cleanaway contract was extended and renewed after the accident. 62 The plaintiff's case with respect to the type of bin lid was, in effect, that Ms Muir's recollection of a plastic lid was faulty and likely affected by the pain killing drugs that she had to use because of her shoulder. The evidence of Reibel and Wilkes that the lid was steel, it was said, should be preferred and the evidence of Mr Dixon disregarded. 63 While Ms Muir was prescribed pain killing drugs in the form of slow release morphine there is no evidence as to what effect it could have or did have on her memory of the accident. 64 Ms Muir was the person most directly affected and interested in the way that her accident had occurred. In her civil action against the MHSB her case was consistently that she was injured while trying to open a plastic lidded bin. Mr Dixon was directly responsible for the contract with Bentley Hospital and was interested in seeing that the requirements of the contract were carried out. With respect to identifying the type of bin and bin lid I prefer the evidence of Ms Muir and Mr Dixon. (Page 16)
The Physics of Opening a Dumpster 65 In order to understand and explain several of the factual issues here it is necessary to refer to at least some rudimentary principles of physics involved. I will do so using the diagram prepared by one of the expert witnesses, Dr Ackland, and tendered as Exhibit 78. The Exhibit appears as Annexure 1 to these reasons. 66 Exhibit 78 was prepared by Dr Ackland in order to try to calculate the point along the bin lid that a woman of Ms Muir's height would be able to reach in order to lift or push the lid into its open position. 67 Because of the uncertainty as to which type of bin was in fact involved in Ms Muir's accident there are many, many pages of expert reports and calculations devoted to bins that were not the kind of bin that caused Ms Muir's accident. Dr Chew's original report (Exhibit 52) concentrated on a Cleanaway bin of the kind that has been described as "low profile". These bins were lower at the front (1140 millimetres) than at the rear (1630 millimetres). It would appear that the centre of the bin lids rotational axis was somewhat lower, being 1480 millimetres. That point would represent the centre of the pin of the hinge: see Exhibit 76, report of Dr Ackland dated 27 November 2003, section 2, and Exhibit 52, scanned images 1 and 2 at pp 6 – 7. Those heights include wheels that the bin sits on. 68 One of the somewhat surprising features of this case is that many of the calculations depended upon and assumed the correctness of dimensions measured by witnesses as opposed to, for example, shop drawings. As will be seen there are some small variations in the references to the sizes of various bins. In some cases the differences cannot be explained by obvious modifications. Whether the differences in some of the measurements were the result of minor error or inconsistencies in the manufacture of bins was not something that was explored in the evidence. 69 For reasons that I will set out below I find that the bin that was in fact involved in Ms Muir's accident was pretty much as drawn by Professor Stone in Exhibit 78. That is, it was 1200 millimetres high at the lid hinge and without wheels. The length of the lid from the hinge to the front of the bin was measured by one of the experts at 1490 millimetres. 70 Exhibit 78, as Professor Stone's notes illustrate, shows the lid at an angle of 63 degrees to the horizontal. The evidence was that that was the angle at which the lid rested when it was locked in its fully opened (Page 17)
position. A worker who wanted to open the bin lid to that position would stand at the front and lift upwards with both hands. Because the lid is hinged at the rear the worker has the benefit of a lever effect so they are not required to lift the full weight of the bin lid. The centre of the mass of the lid will be somewhere around its midpoint. The pin of the hinge is the centre of the lid's rotational axis. The worker opening the bin lid at the front of the bin obtains a mechanical advantage of 2 to 1: that is, they effectively only have to deal with half of the weight of the bin lid. The hinge at the back of the bin lid acts as the fulcrum of the lever in much the same way as the wheel of a wheelbarrow. 71 Of course the force of gravity acting on the bin lid gives it the weight which is perceived by the worker opening the bin. The force of gravity always acts vertically. So long as it is possible for the worker to stand in a position to apply a force to the front of the lid that is exactly perpendicular, that is, at a constant right angle to the line of the side of the lid and not the bin, they get the full benefit of the lever effect. The force required to continue lifting the lid, and of course its apparent weight, would progressively diminish as the lid was raised. 72 The initial force required to open the lid at its end has been measured. The measurement was obtained using a device called a Salter spring scale. Simply put, the weight of the lid can be measured and by using an appropriate formula, converted to a measurement of force. The measurement of weight obtained at the initial opening position is 7.1 kilograms. That converts to 69.9 N. Contrary to submissions made by counsel for Cleanaway, that is a measurement of static force. The force of gravity and the force pushing against gravity are in equipoise when the lid end is weighed. If the force acting against gravity increases the lid will rise. If that force diminishes, the lid must close and ultimately come to rest on the top of the bin. 73 As is apparent by looking at Annexure 1 it is physically impossible for any normal human being to be able to push the lid into its fully opened position from the front of the bin. It must also be remembered that the measured angle of 63 degrees represents the position of the lid at rest on its locking mechanism. In fact, it is necessary to push the lid somewhat beyond that, as Ms Muir reported. 74 To actually be able to push the lid into the fully opened position a worker walks to the side of the lid (after the initial lift at the front) and begins to push there. As soon as they move from the front of the lid at 1500 millimetres away from the hinge, and begin to move towards the (Page 18)
hinge "walking" the lid up the side, the lever effect is diminished. However, as the lid rises its centre of mass shifts towards the axis of rotation at the hinge. If a worker continued to push at say 1 metre along the lid from the hinges, the force needed to lift the lid would continue to diminish as it rose. 75 The question as to whether the F block bin had wheels or not was relevant to the height of the bin at the time that Ms Muir had her accident. The height of the bin was of interest to the parties in the context of an attempt to reconstruct the forces that might have been involved in Ms Muir's accident. That is, the lower the bin was, the farther back from the hinge of the bin Ms Muir should have been able to stand and lift the lid high enough to get it into its latching position. The farther back that she was standing at the time of her accident, the lower the forces involved because of the lever effect. 76 Ms Muir said nothing about whether the bin had wheels or not but described the height of the lid as being "probably about chest high". 77 The evidence of Mr Pratt was that wheels were only provided with bins where it was necessary to place the bin in a position where trucks couldn't gain access and wheels were needed so the bins could be moved manually. He also said that it was cheaper for Cleanaway to provide bins without wheels because the wheels were cast iron and readily damaged. He described the process of giving directions to Cleanaway's operation staff to arrange for the delivery of bins when a new contract was obtained. His evidence was that unless wheels were expressly requested they were not provided. By reference to the service contract forms (Exhibits 15, 16 and 17) he said that the three bins for Bentley Hospital were provided without wheels. Mr Dixon's evidence was to similar effect. 78 Of course, whether the bins had wheels or not does not necessarily resolve the question as to the actual height of the top of the bin that Ms Muir was using when she was injured. As photographs to Dr Chew's report show, sometimes bins without wheels are placed directly on the ground (Exhibit 55) and sometimes they may be raised off the ground by a base other than wheels (Exhibit 54). 79 The photographs annexed to Jenni Miller's report (Exhibit 81) show a man just an inch shorter than Ms Muir, and a bin of the kind that it is probable that Ms Muir opened, albeit fitted with castors or wheels. The bin illustrated in photographs 3 to 5 is at the level of the man's nose. Even looking at the level of the top of the bin (that is excluding the lid itself) (Page 19)
the height of the top of the bin is still at the man's chin. Even allowing for her extra inch of height it seems unlikely to me that a flat topped bin with wheels could have been "chest high" for Ms Muir. It seems probable to me, relying on her evidence, that the bin she opened and which caused her accident was a bin without wheels, resting either on the ground or some other low base. 80 Exhibit 78 was prepared to provide support for the proposition advanced on behalf of Cleanaway that Ms Muir would have been able to stand back and push, almost at the mid-point of the bin lid so as to lift the lid into its open position. At least that was how I understood it when the document was introduced in the examination of Dr Ackland in this way: "Professor were you last night requested to provide a calculation in relation to the – to a distance of 70 millimetres from the hinge end to which an average size person would have the capacity to reach? - - - at 70 millimetres, yes." (at T235) 81 In response to further questions, Dr Ackland acknowledged that he had been provided with input data about the height of the bin lid hinge, shown on Exhibit 78 at 1200 millimetres and he said "I was asked to calculate the height above ground of a point 700 millimetres from that hinge when the bin was opened at 63 degrees to the horizontal." He confirmed, as shown on Exhibit 78 that that height is 823.7 millimetres: at T236. Dr Ackland continued, referring to some of the information about average height and reach referred to on Exhibit 78 as well as his calculation of the height of a point in the lid 700 millimetres away from the hinge with a lid at an angle of 63 degrees: 82 It will be observed that the height used for the purpose of this calculation, 1200 millimetres, assumes that there were no wheels on the (Page 20)
bin. As will be seen, a calculation of the "normal" force applied to the bin lid at a point 70 centimetres from the hinge yields a force of just 67 N. 83 I will return to this matter in the discussion that follows with respect to expert opinion evidence.
Expert evidence: Miller's report 84 Jenni Miller was called as an expert witness for Cleanaway. Her letter of 1 February 1996 to Cleanaway together with a report that she prepared in January 1996 were tendered: Exhibits 80 and 81. At the time Cleanaway engaged Ms Miller to prepare her report, she held a Master of Science specialising in ergonomics, among other qualifications, and she had worked since about 1990 as a consultant in that field. In her report, Jenni Miller describes her assessment of two flat top bins, one steel and one plastic lidded. Both bins were on wheels and both had the same dimensions – 1470 millimetres high, 1810 millimetres long, and 1435 millimetres deep. Both lids were divided in two, pivoting along a hinge at the rear of the bin. 85 Miller observed the opening of bin lids being demonstrated by a Cleanaway employee. This employee, who appears in a series of five photographs attached to the report, was 5 foot 4 inches or 1.63 metres tall. While that was obviously on the short side for a man, as Miller notes, that height was in the 50th percentile for women. That is, it was an average height for a woman. 86 Miller describes the method of lifting that she saw demonstrated. The opening began with the user standing at the front of the bin using one or two hands. She said "as the height increases beyond reach, the user moved to the side of the bin, continuing to push up on the side of the lid, using both hands." … the lid is pushed up to a height which clears the metal projection inside the bin, and then lowered minimally to rest in the fully open position with the strut resting on the projection. The way in which "both hands" might be used is perhaps clarified by Miller's description of the lowering of the lid, "with the user 'walking' his hands down the side of the lid towards the front." This suggests, reasonably in my view, the use of one hand after another. 87 Ms Miller measured "the force required to initiate the movement of the lid." That is, it was the force required to raise the lid even a few millimetres from the surface of the bin. For steel lids Ms Miller measured the force required as "12 kg, that is 120 Newtons." Ms Miller records that the "force required to initiate movement of the plastic lid was measured to (Page 21)
be 7 kgs, that is 70 Newtons." If it were possible to continue to lift from the very front of the lid those would be the maximum forces required. 88 The plastic lid, unlike the steel lids, did not have a small handle on the front to commence the opening. However, there was a 30 millimetre indent under the length of the lid that allowed fingers to be hooked underneath it. After the opening was initiated at the front of the bin, the manner of lifting was otherwise similar to that of steel lidded bins. 89 As I told counsel in the course of submissions, it appeared to me that the photographs annexed to Ms Miller's report were of greater assistance in several respects than the photographs of "simulations" that were taken after Ms Muir was injured. Primarily that was because, according to the captions of the photographs, the photographs record the actual opening of the bin lid as opposed to a photograph of someone merely modelling the behaviour with the bin lid in its latched position. The photographs annexed to Ms Miller's report show the process of opening the bin lid being performed by an employee of Cleanaway who might be expected to be familiar with the bins and experienced with their operation. Finally, the photos annexed to Ms Miller's report were taken before any dispute arose as to how Ms Muir was injured. 90 In her report, Ms Miller refers to the manual handling Code of Practice produced by the Western Australian Occupational Health, Safety and Welfare Commission. That document was Exhibit 8 at the trial. Ms Miller refers to some of the advice contained within the manual handling Code of practice at 4.23: "For lifting, lowering or carrying loads: (b) some evidence shows that the risk of back injury increases significantly with objects above the range of 16 – 20 kgs, therefore, from the standing position, it is advisable to keep the load below or within this range." 91 In the context of her discussion about the Code Ms Miller concludes that "the forces to initiate the movement of the bin lids would not be considered excessive." That is, as she points out in her report, even the "lifting of the steel lid measured at 12 kgs is below this limit of concern". That is of course literally true, with the caveats that the advice at 4.23 refers specifically to a significant increase with respect to the risk of back injury and the weight she refers to is measured at just the initial point of lifting. The rate she refers to was measured by her at just the initial point of lifting. Nor does Ms Miller address the fact that, according to Dr Chew (Page 22)
and as seems apparent from the text and illustrations of the Code, the 16 to 20 kilograms referred to in 4.23 is in the context of loads being lifted with two hands. 92 Quite obviously the type of lift involved with the bin lid is one where the upper body and in particular the shoulders and arms are used. Ms Miller does note that in fact: "… the shorter the person is, the more the movement will occur above the shoulder, with those muscles on a stretch. Thus there will be greater strain placed on a shoulder and upper back musculature of the shorter user. Because of the position of the load relative to the user's body, the lifting action in this case, which takes place at approximately shoulder height for the 50th percentile male and above shoulder height for the 50th percentile female, it would be expected that any risk of injury would be to the shoulder musculature, rather than the back." 93 Miller's ultimate conclusion foresees a risk of harm that on its face had nothing to do with injury to the shoulder: 94 What Ms Miller did not address was the advice contained in the manual handling Code that manual handling above shoulder height does not merely shift the risk of injury from the back to the shoulder but rather is an indicator of increased risk of injury generally: Exhibit 8 at par 4.13, figure 3, and par 4.20. 95 Similarly, Ms Miller's conclusion that "because of the position of the load relative to the user's body, the lifting action … takes place at approximately shoulder height for the 50th percentile male and above shoulder height for the 50th percentile female … " seems somewhat difficult to understand. That would seem to be correct for the initial lifting at the front of the bin at a height of 1470 millimetres (or 58 inches). (Page 23)
However, after the lift commences the location of the load, which is a focus of concern of the Code of Practice (at par 4.20), moves above shoulder height. As the photos annexed to Ms Miller's report illustrate the "load" is not merely above the shoulder of a 5 foot 4 inch (that is 1.63 metre) tall employee but is very quickly above head height. Photograph 5 and its caption illustrate that the 5 foot 4 inch (or 1.63 metre) tall Cleanaway employee "has to stand on his toes to reach with his right hand." 96 Ms Miller's report was sent to Mr Pratt along with a covering letter dated 1 February 1996: Exhibit 80. In her letter she says, among other things: "As discussed, reach concerns are not of real importance. The bins were not designed to be opened with the user standing at the front for the full excursion of the lid. The design means that the user will walk along the side of the bin, pushing up on the lid. Shorter users may have to stand on their toes when the lid is fully opened, but this is not a reason for damming (sic) the whole design. The force requirements are within the recommendations of the manual handling code of practice. Obviously the plastic lidded bins require less force and would therefore be preferable. However, I would not consider that the force required to open either type of lid was excessive. The design of the bin would be better with a lower front edge, so that the user did not have to lift the waste to near shoulder height. However, the design of many things can be improved without implying that what exists already should be immediately discarded!" 97 Ms Miller's lack of concern about short users being forced onto their tiptoes is somewhat troubling. As Dr Ackland said in his evidence, the fact that a 5 foot 4 inch user is forced onto their toes in order to open the lid means that the bin has not been designed to account for the 5th to the 95th percentile of human beings. He said that a person should not have to stand on their tiptoes to engage the lock and should be able to do so from a standing position.
(Page 24)
98 In her covering letter, Ms Miller also addresses the issue of "roll top bins" and the pushing and pulling needed to open and close this type of bin lid. She measures the pushing force with respect to these lids at between "7 and 12 kg, that is between 70 and 120 Newtons".
99 Having had the benefit of hearing from the other expert witnesses called in this case in my view Ms Miller's assessment was not carried out with a great deal of attention to detail. Counsel for the plaintiff argued that Cleanaway should have known that that was so merely by reading Ms Miller's report.
Expert evidence: Dr Chew, Dr Ackland and Professor Stone 100 The parties tendered two lever arch files of expert reports on the subjects of engineering and ergonomics. It was a considerable volume of material which ultimately showed that the parties were in the proverbial furious agreement with respect to the calculations of forces that potentially or theoretically could be used to open a plastic lid on a flat top dumpster bin. The real issue between the expert witnesses was as to how a worker like Ms Muir would in fact have gone about opening the bin lid either generally or on the day that she was injured. Reduced to its essentials, this dispute was effectively about where Ms Muir stood or could have stood, where along the side of the bin lid she actually pushed, and in what direction she pushed to heave the lid into its locked open position. 101 Dr Chew is a chartered professional engineer with a PhD in mechanical engineering. He is a certified professional ergonomist and is a member of several learned societies. He was put forward as an expert in the field of both engineering and ergonomics and his qualifications were not challenged. 102 I do not propose to refer to all of the reports of each expert but rather to illustrate the reasoning process and observations that led each to the conclusions that they reached. Dr Chew prepared six reports with respect to matters in issue in this action. For Dr Chew's first report dated 10 April 2003 he was provided with certain instructions with respect to Ms Muir and her 1996 accident and asked to measure the forces involved in lifting plastic bin lids. He attended at the Bentley Hospital, inspected a waste bin and measured the forces involved. From his report, including photographs, it is obvious that the bin that he inspected was one of the "low profile" bins introduced after Ms Muir's injury. (Page 25)
103 Dr Chew measured the force required to open the right lid of the bin at various points down the right side of the lid commencing at 50 centimetres from the rear hinge right down to the front of the lid at 150 centimetres from the hinge. The measurements were taken using a Salter spring scale. The results that Dr Chew obtained illustrate the effect of the lever principle. Attempting to lift the lid at 50 centimetres from the hinge yielded 24 kilograms (or 235 N of force). Lifting it at the front edge gave only 8 kilograms (or 78 N of force). 104 Dr Chew's instructions led him, correctly, to understand that Ms Muir commenced lifting at the front edge and continuing the lift by walking down the right side of the bin while exerting an upward lifting force. He was told to assume that Ms Muir was 5 foot 5 inches tall and weighed between 85 and 90 kilograms. Based on information he received from Ms Muir he assumed that the final lift, to put the lid into its locking position, took place with Ms Muir lifting vertically upward with her right hand approximately 500 millimetres from the lid's hinge. 105 This led him to conclude that the lifting forces that she would have used would vary between 78 to 235 Newtons. 106 Dr Chew also carried out an "indicative biomechanical analysis". This analysis used software created by the Centre of Ergonomics at the University of Michigan ("3D SSPP software"). The software is based on a three dimensional biomechanical model and calculates the reactive force movements at six body joints and one location in the back when a force is applied by a person's hands. Dr Chew performed this analysis to obtain an indicative ergonomic assessment of the task of lifting a bin lid. 107 The program requires that the user input various criteria including the posture adopted by the subject of analysis. Dr Chew based those inputs on the photographs that he had been provided of Ms Muir. Based on his assessment that forces up to 235 N would be required to lift the lid, and using the body posture demonstrated by Ms Muir, the 3D SSPP software analysis reveals that hardly any female workers would have sufficient shoulder joint strength to apply the 235 N lifting force "with the body posture under consideration". From this Dr Chew inferred that there was a very high risk of injury to the right shoulder when 235 N of lifting force were exerted in that body posture. 108 Dr T R Ackland was briefed by the defendant's solicitors to respond to Dr Chew's report. Dr Ackland was offered as an expert in the fields of biomechanics and ergonomics. He obtained a doctorate in physical (Page 26)
education at the University of Western Australia, his area of research being biomechanics. He is a tenured professor at the University of Western Australia teaching in fields related to human anatomy including biomechanics and ergonomics. 109 Dr Ackland was critical of Dr Chew's report for several reasons. For his first report, he examined a bin similar to that described in Dr Chew's first report, that is a low profile bin: Exhibit 76. The bin was examined at the defendant's premises with the assistance of one of the defendant's employees "Nick". Nick was apparently only 154 centimetres tall, that is about 10 centimetres less than Ms Muir. 110 Dr Ackland challenges the assumption made by Dr Chew that Ms Muir's hand would have been lifting at a point 50 centimetres from the hinge of the lid. Dr Ackland says: "Even at 10 centimetres shorter in stature than Ms Power, Nick is clearly able to support the lid with the right hand at 60 centimetres from the hinge and the lid held at + 50 degrees to the horizontal in order to lock the support stay … one can confidently assume that Ms Power could adopt the same posture as displayed by Nick but with her support arm positioned at 70 or 80 centimetres from the hinge." 111 Of course, both Dr Chew and Dr Ackland were acting on the mistaken assumption that it was a low profile bin that was opened by Ms Muir at the time of her accident. 112 In referring to photographs of Ms Muir attempting to recreate the manner in which she was injured, which were included in Dr Chew's report, Dr Ackland says: "She is depicted in these images as having used her right arm to support the lid. In a more realistic simulation (ie when supporting the weight of the lid) this would be a most unnatural posture to adopt, since Ms Power's left arm would need to cross in front of the body and reach out maximally to control the support staff. This is not an impossible action to perform, but not one that one would naturally or normally undertake." (Page 27)
113 Dr Ackland performed his own measurements of the forces involved in raising the lid. He also used a Salter scale. He said: "Assuming the lid was opened slowly (ie without a jerky motion), the initial forcer required to open the lid from the end was measured as 7.1 kg or 69.9 N. Using this value the force required to support the lid at various opening positions (Fn) can be estimated. This has been done for an operator who, theoretically could raise the lid to the 'fully open' position by standing at the front of the bin …" 114 Dr Ackland did not challenge the physical measurements of force obtained by Dr Chew. However he was critical both of Dr Chew's conclusion as to the force said to have been used by Ms Muir and also the results of the 3D SSPP simulation because, among other things, Dr Chew: "… incorrectly specified that the hand load acts vertically. To the contrary when opening the lid, a person clearly applies a force 'normal' to this lid (ie perpendicular to the lid). This would greatly effect the resultant output from the 3-D SSPP simulation for the shoulder joint." 115 I have referred to Dr Ackland's measurement of 7.1 kilos taken with the lid in the near closed position at the front edge. That, like some other measurements taken by Dr Ackland, was a measurement of static force: Exhibit 76 table 1. Dr Ackland also took a measurement of the static force with the lid at 50 degrees to the horizontal, at 50 centimetres from the hinge (14 kilograms or 137.2 N) and 100 centimetres from the hinge (9.2 kilograms or 90.2 N). These measurements represented what Dr Ackland described as a "normal" force, that is, a force at right angles to the lid. 116 Thus, by assuming that, unlike "Nick" Ms Muir would in fact have lifted the lid at a point 70 or 80 centimetres from the hinge and with a force precisely perpendicular to the lid Dr Ackland derived estimates of the force required to lift the lid of the low profile bin that were substantially less than those of Dr Chew. For these two reasons and also because he criticises the adequacy of the inputs used by Dr Chew, Dr Ackland concludes that the 3D SSPP analysis is clearly "invalid". Dr Ackland performed no such analysis himself although it seemed he had the means to do so. (Page 28)
117 Dr Ackland reached a number of conclusions "based on the information provided to me and the data collected at the site visit on 20 November 2003, as well as my 12 year's experience as consultant ergonomist". Dr Ackland was slightly more circumspect in referring to the provisions of the Manual Handling Code than was Ms Miller. Dr Ackland says at p 8 of his first report (Exhibit 76): 118 I have already set out the manner in which Dr Ackland challenges the assumptions made by Dr Chew about the way in which Ms Muir actually lifted the bin lid. With the low profile bin lid Dr Ackland concluded that: "… the loads (initially shared by two hands and then supported by one hand momentarily in order to lock the support strut) varied from 7.1 kgs (69.9 N) to 14.0 kgs (137.2 N). This upper load limit is approximately half that used by Dr Chew in his first simulation." 119 It is of course to be anticipated that an expert witness such as Dr Ackland might be able to offer useful evidence based on his collection of data or conclusions that he has reached based on an analysis of that data and any assumptions that he has been asked to make. 120 It is difficult however to give much weight to expert opinion that relies in any significant way on the "years of experience" of a witness. Unless the process of analysis or inference by which an opinion is reached is expressed in a manner which permits the conclusions to be scrutinised (Page29)
and a judgement made as to its reliability, the opinion can carry no weight: Hillstead v The Queen [2005] WASCA 116 at [48] – [49]. The "data collected" by Dr Ackland would appear to amount to this: if a worker applies force at the optimal point selected by Dr Ackland and applies that force in a manner perfectly perpendicular to the bin lid, then the amount of force required by the worker to support the bin lid over their head with one hand is "only" 14 kilograms or 137.2 N. Accepting that both experts were in fact looking at the wrong type of bin at this point, this nonetheless strikes me as a rather bold assertion. No doubt there would be moderately fit men and larger women who would manage a single handed lift of 14 kilograms over their head. I have difficulty however in accepting Dr Ackland's unqualified assertion. 121 Before leaving Dr Ackland's first report however it is necessary to say something about his assumption that any measurement of force used should be calculated as "normal". There may well be something in Dr Ackland's criticism of Dr Chew's assumption for the purposes of the 3D SSPP analysis that the load in the hand of the worker acts vertically. As the photographs annexed to Dr Ackland's report suggest, and as might reasonably be anticipated, when a worker grasps the bin lid their hand naturally pivots on the wrist to conform with the under surface of the bin lid. However even a superficial examination of the photographs figures 3 and 5 in his report will show that the force vector of the shoulder and arm is not "normal". 122 Dr Ackland was also aware that Ms Muir had described her final effort to get the bin lid up into its latched position as "jerking" it up. Despite that, all of his calculations rely on the calculation of static forces. This was despite the fact that he was conscious that "if she'd have jerked on the side of the lid there would have been a much higher force than the static force that we had been measuring": T246. 123 In the course of re-examination, Dr Ackland was invited to further explain his assumption and expectation that the "normal operation of the opening of the lid". Dr Ackland did so by way of analogy of a swinging door: "If I might start by saying if a person were to open a door, they would move as far away from the hinge to open or close that door. They wouldn't try to close that right near the hinge." (Page 30)
124 Dr Ackland agreed in cross-examination that the objective of the force measurement test with respect to the bin lid and the 3D SSPP analysis was to assess risk of injury. He agreed that that was the point of such an analysis although he disputed the validity of the manner in which Dr Chew had carried it out. 125 Professor Brian Stone was also called on behalf of Cleanaway and his report of 11 December 2003 was tendered in evidence: Exhibit 79. Professor Stone holds degrees in engineering and his expertise is in the area of dynamics. That is, his expertise lies in the area of analysing forces and the motion of bodies under the influence of forces. He had no relevant expertise in the field of ergonomics. This however did not prevent him from criticising Dr Chew's report of 10 April 2003 on this basis: "In my view, however, there is a flaw in Dr Chew's analysis. Dr Chew assumes that the arm of the lifter is vertical and the force applied to the lid is vertical. However, this need not be the case and may not have been the case when Ms Power was lifting the bin lid. In the alternative, it is my opinion that it is more likely that the force would have been applied at an angle to the vertical as the lid was lifted." 126 No objection was taken to Professor Stone joining the dispute as to what angle Ms Muir's arm assumed when her shoulder was injured while she lifted the bin lid. Professor Stone did include an equation for calculating force where the force vector is at an angle from the vertical. However, notwithstanding the alternative offered by Professor Stone the results included in his reports only set out the force when measured vertically and the force measured perpendicularly. In his evidence before me, Professor Stone also offered the analogy of the swinging door as proof that Ms Muir would have applied force far from the hinge of the lid. 127 Curiously, despite Professor Stone's area of expertise, no evidence was offered with respect to any measurement or calculation of dynamic force. In fact, beyond merely confirming calculations previously made by Dr Chew and Dr Ackland, Professor Stone's evidence was of little assistance. 128 As the parties expanded their investigations to embrace the possibility that the bin involved in Ms Muir's accident was not the low profile bin described in Exhibits 52 and 76 further expert reports were filed. Whichever type of bin was analysed, the differences between the (Page 31)
parties positions varied depending upon where and how force was applied to the bin lids. The extremes of the opinions offered seemed to me to bracket the truth like the ranging shots of naval artillery. The "re-creations" relied upon by Dr Chew and the demonstration of "Nick" seized upon by Dr Ackland are not terribly scientific. It seems plain enough to me however, relying on the evidence of Ms Muir and the photographs annexed to the report of Ms Miller and figures 3 to 5 annexed to Dr Ackland's first report (Exhibit 76), that it is most improbable that a woman of average height would be able to apply force through her arm perpendicular to the bin lid in the final stages of heaving it into the latched position or do so close to the mid point of the lid. I will deal with the question as to where a person of Ms Muir's height would have applied force to push the lid into its latching position when I come to consider the issue of breach of contract.
Negligence 129 The plaintiff seeks to recover all or part of the compensation and common law damages that it paid to Ms Muir by claims made pursuant to s 7(c) of the Contributory Negligence Act and s 93(1) of the Workers Compensation and Rehabilitation Act1981. Either claim requires a finding that negligence on the part of Cleanaway caused Ms Muir's injury. 130 There can be little doubt that there was a foreseeable risk of injury in the undemanding sense described in Wyong Shire Council v Shirt (1980) 146 CLR 40. As Mr Dixon said in his evidence, at some point, probably in 1995, Cleanaway had recognised that at least so far as its steel lids were concerned "there were issues". That would appear to be the reason a decision was made to phase them out notwithstanding the advice of Jenni Miller that either steel or plastic lids were ergonomically acceptable. It was not suggested on behalf of Cleanaway that Ms Miller was engaged by way of Cleanaway's performance of the OH & S term. The only sensible explanation for Cleanaway's concern and the engagement of Ms Miller was a degree of concern about the physical capacity of some users to open the lids and the risk of injury of some kind. 131 One of the features of the conduct of this trial was that a number of documents were tendered as evidence by consent, never to be referred to again. One of those documents, Exhibit 73, appeared to be a pamphlet prepared by Cleanaway and distributed to customers. It is entitled "Bin Safety" and the bins depicted in the pamphlet in a number of drawings appear to be of the flat topped plastic lidded variety. The very last suggestion offered, "For the safe use of Cleanaway bins" is with respect to (Page 32)
"Choosing a safe bin". It says "Please ensure that your choice of bin size is appropriate to manual loading issues at your site. Bins that are too tall to load easily will contribute to strain injuries." A cartoon shows someone struggling with the task of lifting some trash overhead to get into the bin, the lid being already opened. The pamphlet is undated. 132 Identifying that there is sufficient risk of physical injury to impose a duty of care is however a modest first step towards finding that there has been negligence. Accepting that a duty of care arose, the next question is what a reasonable person in the position of Cleanaway would have done by way of response to the risk of injury. It is of course only if Cleanaway has failed to do what a reasonable person in its circumstances would have done that breach is established. The perception of what a reasonable person in Cleanaway's position should have done calls for: "… a consideration of the magnitude of the risk and the degree of the probability of its occurrence, along with the expense, difficulty and inconvenience of taking elevating and any other conflicting responsibilities which the defendant may have": Wyong Shire Council v Shirt (supra) per Mason J at p 47. 133 That analysis must not be based on hindsight. Rather, it is only by looking forward from the time before the accident that due weight can be given to the factors identified by Mason J in Shirt: Vairy v Wyong Shire Council [2005] HCA 62 per Hayne J at [127]. 134 So far as the magnitude of the risk is concerned the evidence before me shows, despite the ubiquity of dumpsters, one injury. The kind of injury that might be expected, without diminishing for a moment the particular problems suffered by Ms Muir, seems unlikely to be life threatening. I did not find the 3D SSPP analysis prepared by Dr Chew to be particularly helpful in assessing risk of injury or probability of its occurrence in as much as it seemed to predict that the task of opening the bin lid was simply beyond the physical capacity of many women based on the specific postures that were input. Dr Ackland accepted that a risk of injury could be inferred from results of the kind obtained by Dr Chew but of course disputed the validity of the inputs made by Dr Chew in carrying out his analysis. While I am prepared to accept that what Ms Muir told Dr Chew allowed at least a rough approximation of her posture and actions, I am unable to say what the sensitivity of the 3D SSPP programme is to variations in the information that is input. Dr Ackland's criticism of the use of two dimensions for the posture rather than three (Page 33)
would, in my view, at least warrant the conclusion that the two dimensional calculation is of a lesser order of reliability. 135 Using the 3D SSPP analysis, Dr Chew concluded that a woman of similar height to Ms Muir using a posture similar to that modelled by Ms Muir could safely use her right hand to apply an 88 N pushing force. Similarly, he determined that a 176 N force applied by a similar woman in a similar way was beyond the shoulder strength capability of virtually all women of Ms Muir's height and weight. Dr Chew concluded that beyond a force of 88 N, the force "… would be close to the level above which there is increased risk of injury because of the magnitude of the force, and because the force is applied above shoulder height with a substantial sideway component." By reference to the work of Ayoub and Mital who measured the average force applied by a number of adult men when applied by the right hand held at shoulder height pushing to the right of the body, he concluded that a "corresponding limit for adult women would be 94 N." Dr Chew said in his 8 September 2008 report (Exhibit 56) however that he was not aware of published data which specially addresses the matter of the one handed force exerted by Ms Power (Ms Muir) in the way that she demonstrated to him. 136 Beyond Dr Chew's analysis that suggested particular risk for shoulder injury when a lift of greater than 94 N is performed by a woman the height and weight of Ms Muir in the manner demonstrated by her, it is very difficult to extrapolate to a more general risk. It is difficult, given the sheer number of such bins in common use for decades, to conclude that there is a significant risk of injury based on that evidence and one person's experience. 137 If it were accepted that there was sufficient risk of injury to warrant the imposition of a duty of care with what would appear to be a relatively low magnitude of risk and probability of occurrence the question then arises – what should a reasonable person have done? 138 The plaintiff's pleaded case was that what was required here was that Cleanaway either provide the plaintiff with a platform for its workers to stand on in order to open the lid, or provide a lighter lid, or instruct the plaintiff and its employers about safe work methods, or fit gas struts to the lid to reduce its opening force to an acceptable level. 139 A plaintiff who alleges that there is a reasonable means of alleviating a particular risk has the burden of establishing that that is so: Nelson v John Lysaght (Aust) Ltd (1974) 132 CLR 201. Often commonsense (Page 34)
applied to the available evidence will suggest the reasonableness of the alternative. Frequently however expert evidence will be required. 140 While there is some expert evidence with respect to one of the plaintiff's pleaded alternatives for avoiding the risk of shoulder injury, the submissions made for the plaintiff were rather different. The submission was essentially that with the knowledge that Cleanaway had or should have had in early 1996 it should simply have gone: "Back to the drawing board. Shouldn't have released this bin on the basis that we say that the assessment, if done on the static, dynamic and vertical forces could have produced as a result so much greater then what the request for tender was asking that either they wouldn't have submitted a tender at all or would have had to fashion a bin which was capable of performing at a level which was either formally compliant … or provided an alternative which properly assessed would be sufficient to discharge any ergonomic consideration." 141 In response to an observation that Cleanaway had, prior to supplying bins to the hospital sought professional ergonomic advice and that advice was favourable, the submission for the plaintiff was essentially that Cleanaway should have known that the report was flawed. There was however no suggestion in any question put to either of the former Cleanaway employees who gave evidence that they knew or reasonably should have known there was something deficient with Ms Miller's report. Nor am I able to conclude that there is anything on the face of the report itself that would lead a reasonable lay person to a conclusion about the safety of the bin lid operation that was in conflict with that of an apparently qualified professional ergonomist. 142 I do not accept that the evidence as a whole establishes to the necessary standard that there was a significant risk of injury for users of bins of the kind that I am concerned with here. While I can and do accept that the weight and the dimensions of the bin lid caused the injury to Ms Muir, it is difficult to extrapolate from the evidence before me to a particular level of risk that attaches to the use of a dumpster bin. Against that are all of the obvious functional issues that would have to be taken into consideration in designing a dumpster bin. 143 While not a thing of great beauty the dumpster bin is an object of considerable utility. Its size and robustness allows large volumes of trash to be safely stored and efficiently disposed of. It is a design which, for the (Page 35)
most part, appears to have stood the test of time. While the change to plastic lids was an obvious improvement it is not apparent that the change to low profile bins has eliminated risk of injury of the kind that I am concerned with here. 144 This was not a case where common sense obviated the need for expert analysis of the alternatives being proposed. There was little evidence and much less analysis from the plaintiff of the alternative means that it was proposing. The suggestion of a platform carries with it its own potential occupational health and safety issues as well as issues of practicality in terms of the lifting and lowering of the bin in the process of its emptying. Similarly, the idea of a gas strut was put forward in an offhand way at best. No consideration was given as to either the durability of a gas strut or the consequences of fitting one in circumstances where the bin lid was going to be violently flung open every time the bin was emptied by a truck. Nor was any consideration given or evidence offered as to one of the more obvious consequences of fitting a gas strut. That is, if a large enough gas strut was fitted to assist in raising the lid, what would the consequences be when it came time to close the lid from its full open position? In other words would the alleviation of the risk of injury on the way up translate into an increased risk of injury in trying to bring the lid down? |