POWERCOAL PTY LTD & Peter Lamont FOSTER v INDUSTRIAL RELATIONS COMMISSION OF NSW & Rodney Dale MORRISON
[2005] NSWCA 345
At a glance
Source factsCourt
Court of Appeal (NSW)
Decision date
2005-07-13
Before
Spigelman CJ, Mason P, Handley JA, Walton J, Vice-President Boland J
Source
Original judgment source is linked above.
Judgment (26 paragraphs)
Background Facts 3 The coal being mined was in an area known as '304 panel'. The coal seam at 304 panel was approximately three metres thick and was located between the 'Awaba Tuff', a layer of compacted deposits of volcanic ash below the coal seam and the 'Teralba Conglomerate', a hardened layer of stone pebbles and binding material above the coal seam. 4 Coal is extracted by using a large continuous mining machine, which is 15 metres long with a 3.6 metre wide cutting head or drum. The continuous miner is operated remotely by an operator who stands towards the rear of the machine on its right hand side and drives it into the coal. Once the coal has been extracted from the coal face it is loaded onto a shuttle car which discharges its load at a collection point some distance from the mining operation. 5 There are two distinct stages to the mining process. The first, called the first workings, is where the continuous miner is driven into the coal to create underground roadways, called "headings" and "cut throughs", of approximately 5.5 metres in width and varying height depending upon the height of the coal seam. Headings are the primary drives undertaken into the coal deposit by the continuous mining machines. Cut throughs are the cross drives later performed at an angle, usually of 90 degrees, to the headings, thereby forming a squared pattern of roadways. The formation of headings and cut-throughs leaves residual pillars of coal, which support the layer of conglomerate above. Accordingly, after the headings and cut-throughs have been mined in an approximately squared formation of tunnels, the layer of conglomerate lies across the mined area and the remaining pillars, forming a more or less continuous roof, supporting the terrain above and supported itself by the residual pillars of coal. Where necessary during first workings, this roof structure is given additional support by using roof bolts and 'W straps'. A W strap is a piece of metal of a metre to a metre and a half in length, which is extended across the rock and bolted in place. 6 The second stage of the mining process, called second workings, is where the coal is mined out of the residual pillars of coal that have been left by the first workings. There are two methods of pillar extraction. One involves removing the whole of the pillars and is called total pillar extraction. The other method is more conservative and involves extracting approximately half of the coal from each pillar in a sequence of drives known as 'lifts'. Each lift involves the continuous miner cutting a designated distance into the pillar. Approximately half of each pillar is extracted and the other half is left standing. This method is known as 'pillar stripping'. 7 Where a pillar has been removed or stripped the roof above it is unsupported and is expected to fall soon thereafter. The void so created in the area where the coal has been extracted from the pillars is called the goaf. In order to ensure the safety of the miners, pillars are stripped through a process called 'retreat mining', which involves retreating backwards from the deepest point within the mined area along the headings, towards the exit to the mine. The nature of retreat mining is that, as the goaf area is created, the miners retreat back from it, thereby ensuring that, while working, the miners remain under a roof structure which has been appropriately supported, usually by roof bolts, during first workings. As the continuous miner proceeds through its lifts along a particular pillar, timber props are installed as roof support along the area which previously formed the cut through on one side of the void or goaf area. Thus, in second workings, there are two distinct areas: the goaf area and the work area. None of the miners are allowed to go into the goaf area for any purpose. The roof in the goaf area is unsupported and is designed to fall. The roof in the work area is supported with timber props and roof bolts and is designed to stay up. 8 An integral part of the retreat mining process is to leave behind a reduced pillar of coal in the goaf area, known as a 'stook'. The stook serves two important functions. First, it acts as a minimum support for the roof in the goaf area. Secondly, it forms a barrier between the goaf area and the work area and will break off any roof fall in the goaf area before it enters the work area. Thus, as the miners retreat backwards, extracting coal from the pillars, some small pillars of coal are intentionally left behind at the end of each of the extracted area to support the roof and protect the roadway upon which the miners retreat from any roof fall in the goaf area. Stooks are vital in both 'total pillar extraction' and 'pillar stripping'. 9 On 18 May 1998 Mr Foster, the manager of the Awaba colliery, applied to the Department of Mineral Resources ("DMR") to retreat out of 304 Panel and 14 SW Heading by the pillar strip method for the purpose of extracting the pillars of coal which had been left behind by the first workings, some years previously. Pillar stripping had been used at the Awaba colliery since September 1997, when it was introduced to replace total pillar extraction, for safety reasons. 10 On 20 May 1998 the DMR approved "General Rules Pillar Stripping" for 304 Panel and 14 SW Heading. A working plan for the pillar stripping in 304 Panel was produced on 13 July 1998. Panel 304 was to be mined in a series of sequences, the first two of which were sequences 4 and 5, which measured about 65 metres in length. Sequences 4 and 5 involved cutting into a solid wall of coal situated between two dead end headings, called "stubs" at 1 Heading and 3 Heading, using approximately 17 lifts. 11 A conglomerate roof is generally firm and strong and does not usually require extra support. However, during the first workings in 1 and 3 Headings at 25 Cut through in 304 Panel, some years previously, poor roof was encountered, and extra roof support was installed consisting of 6 scatter bolts with butterfly plates at 1 Heading and 4 W straps each with 5 bolts about 1 metre apart at 3 Heading. This indicated that the miners originally involved in driving the heading must have determined that the roof in that particular area required additional support in order to ensure its integrity. In addition, the working plans showed that the area in which the work team was working had a fault of 0.3 metres running diagonally across it. Faults in the conglomerate can occur where there has been a shearing of the terrain in a vertical fashion such that the conglomerate does not form a continuous layer but has been either lowered or raised by the shearing effect. The thickness of the conglomerate has an effect on its strength and ability to bridge open areas and support the terrain above. 12 Before any work commenced on 15 July, Mr Cull, the Technical Services Coordinator, tested the roof at 1 Heading and 3 Heading and determined that the condition of the roof presented no concern. 13 Between 15 and 16 July a team consisting of Mr Gardner (a mine deputy) and miners Ian Miles, Warren Etheridge, Kevin Dunn, Alyn Gear, Barry Edwards and Greg Cornwell extracted the majority of the coal required to be stripped from the relevant pillars. On 17 July the team of miners were engaged in completing the last two lifts of coal from the pillar. Before commencing work on 17 July, the mine Deputy for that shift, Mr Gardner, performed checks of the work area, which he was required to do under the Coal Mining Regulation Act. Mr Miles, a union appointed Check inspector, and the holder of a mine deputy's ticket, also checked the work area and, following some doubts as to its condition, "sounded the roof". 14 Sounding the roof involves striking the roof with a drill steel to determine the condition of the roof. A poor roof will create a particular sound. When sounded by Mr Miles, the roof sounded good and as a result, work commenced. During the course of the morning Mr Miles observed that he felt uneasy about the condition of the roof and sounded the roof again on a number of occasion. On each occasion he determined that it was safe for work to continue. 15 The team of miners, who were all experienced and some of whom sounded the roof themselves, all gave evidence to the effect that they had independently formed the view that there was nothing in the roof that would prevent the work from proceedings as planned. 16 The mining plan required a stook, called stook X, to be created on the right hand side of the layout of 4 and 5 sequences. Stook X was to be a minimum of 1.5 metres in thickness between the goaf area created by the extraction process and the stub end of 3 Heading. Stook X was intended to create a barrier between the goaf area and the roadway along which the miners were retreating. 17 For reasons that are unknown, instead of creating stook X the miners extracted the coal out of the area that was to have been stook X and in so doing reduced it to approximately 20% of its intended size. This was evocatively described by one witness as 'robbing the stook'. There was no evidence to explain why stook X was mined improperly, without warning and contrary to the mining plan. The effect of 'robbing stook X' was that there was an inadequate barrier between the goaf area and number 3 Heading. Instead, a section of the roadway became part of the goaf. The void created by the substantial removal of the two pillars forming sequences 4 and 5 was the subject of a major roof fall. Barry John Edwards, who was operating the continuous miner, and who was engaged in the unplanned and unauthorised removal of stook X, was struck by falling rock and fatally injured.