7 The installation of the Pipeline involved significant civil engineering works. It was installed at depth and was buried, except for its outlet which passed through a headwall constructed close to the bed of the unnamed creek.
8 At its upper or inner end where it is located to capture groundwater, the invert of the Pipeline is 16.6 metres below ground surface. At this depth the Pipeline is inaccessible for all practical purposes. Located near to its inner end is a pump. That pump has the capacity to control the groundwater level relative to the invert of the Pipeline by pumping groundwater to a dam or dams on the surface.
9 Until 1996, coal tailings from the coal washing plant were directed to a tailings dam or dams located on the mine site. As the volume of these tailings increased, so the area required for tailings disposal also increased. Recognising the need to limit the area required for further tailings disposal, Powercoal developed a plan that would avoid the need for this ever-increasing surface area.
10 It proposed to disposal of tailings and mine water through bore holes leading to old underground workings in a disused coal seam. The area of intended disposal was hydraulically connected to the area in which the inlet to the Pipeline was located.
11 Powercoal subjected its proposal to risk assessment prior to implementation. In a report prepared in April 1996, the displacement of existing water within the mine workings by the increased volume of water and tailings proposed to be deposited in those workings was recognised. So also was the possibility that this displacement would result in discharge into Stony Creek through the Pipeline. Having recognised that possibility, the report continued -
"Due to the distance and unknown condition of underground roadways, residence time of the tailings and water from the bores is unknown, however given the nature of tailings flow, storage area and distance it is unlikely that these flows will directly reach the discharge point. However the displacement of water in the workings may occur. Generally flow from this point only occurs in exceptional and extended rain events. As this is the only point the water can discharge from the workings a weekly inspection to determine, flow, pH, conductivity and NFR will be undertaken. Monitoring these parameters will enable determination of any change in the water flow or quality."
12 Powercoal implemented its tailings disposal proposal in 1997. Tailings in the form of a slurry with a 30 percent solids content were directed through two bore holes into the old mine working areas. It seems that the monitoring recommended in the risk assessment report was undertaken for a time but ceased in 1998 following reports that "only clean water" was discharged via the Pipeline into the unnamed creek above Stony Creek.
13 Subsequently, Powercoal proposed to extend underground coal mining at the Newstan Colliery and to upgrade surface facilities. For this purpose it sought development consent from the Minister. As it was required to do, it prepared an environmental impact statement (the EIS) in support of its application. The process of discharging coal tailings slurry underground and its consequence for discharge from the Pipeline was identified and discussed in that document. It states (at p 3.24):
"Mine and slurry water pumped underground will eventually build up and discharge from the seam outcrop at a constructed discharge point in the catchment of Stony Creek. The length of flow path, the undulating bed profile of the old mine workings and the extensive storage time, will prevent discharge of suspended material or other contaminants. Regular monitoring of discharges from the constructed discharge point is undertaken (refer to section 5.3)."
14 Notwithstanding the reference to section 5.3 of the EIS in that passage, it is accepted by the parties that section 5.3 refers neither to the Pipeline discharge point nor to any monitoring having taken place at that discharge point.
15 On 14 May 1999, the Minister granted conditional development consent to Powercoal for the Newstan Life Extension Area Project (the LEA development consent). Condition 4.1(a) of the consent required that before commencing construction of any new surface facilities, Powercoal was required to prepare a water management plan in consultation with nominated government agencies, including the prosecutor, and to do so to the satisfaction of the Director-General of the then Department of Urban Affairs and Planning. A plan prepared in apparent conformity with that condition was provided to the Director-General in November 1999. It is not suggested that the water management plan then submitted did not meet the requirement for "satisfaction of the Director-General".
16 Neither condition 4.1 of the LEA development consent nor any other condition of that consent required that a water management plan include reference to the Pipeline or the monitoring of discharges from it at the unnamed creek. Moreover, the water management plan prepared by Powercoal in apparent compliance with the development consent contained no such consideration.
17 As I have earlier indicated, monitoring occurred in the unnamed creek at the discharge point from the Pipeline between October 1996 and July 1998. This involved weekly monitoring but apparently with no record of any "dirty water" discharge during that time. Indeed, the evidence reveals that there is no recorded instance of dirty water discharging from the Pipeline into the unnamed creek from 1976, when the Pipeline was installed, until the incident which gave rise to the present charge against the defendant. This is the case notwithstanding the existence of records demonstrating that ground water within the mine workings rose above the level of the invert of the Pipeline on many occasions following its installation.
Operation of Newstan Colliery: post 2002
18 The defendant is a subsidiary company of Centennial Coal Company Limited (Centennial Coal). In 2002 Centennial Coal acquired all of the assets of Powercoal when the NSW Government submitted Powercoal's assets for sale by tender. The assets acquired by Centennial Coal included the Newstan Colliery. The defendant was the corporate vehicle identified by Centennial Coal to operate the newly acquired Colliery.
19 Following acquisition in 2002, the defendant continued the tailings and water management practices for the Newstan Colliery that had been adopted by Powercoal. Those practices included the storage of tailings and mine water in the old underground mine workings; the monitoring of the underground water level via the bores located in the seam hydraulically connected to the Pipeline inlet, and otherwise implementing the 1999 water management plan that had been prepared in accordance with the LEA development consent.
20 It was not until 2007 that the defendant ceased the underground disposal of tailings into the old mine workings. Instead, it developed a surface storage facility which involved the retention of solids at the surface and the pumping of decanted water from those solids into the underground mine workings. This facility was developed and constructed by the defendant at a cost of $7.35M.
21 At the time of mine acquisition in 2002, Powercoal held Environment Protection Licence 395 (EPL 395) issued under the provisions of the POEO Act. EPL 395 was transferred to the defendant following acquisition. It was required to be held because the activities carried out at the Newstan Colliery are "scheduled activities" within the meaning of the POEO Act, involving the operation of coal mines, coal works and waste facilities/coal wash landfill.
22 By notice given to it in February 2008, the defendant was required by the prosecutor to prepare and submit by 30 June in that year a revised water management plan. The requirement for that plan included the following:
"b) A revised water balance and water storage plan for both the northern and southern sectors of the premises that has the following objectives;
i) Minimising all water discharges from the premises at any time by efficient water management methods, such as maximising all opportunities for on-site water use, spray irrigation and water storage;
ii) Minimising all discharges of 'dirty water' from the premises at any time;
iii) Ensuring that activities undertaken by the mine do not pollute waters.
…
The EPA will use the information in the RWMP to further revise the water discharge and monitoring conditions in the licence."
23 In compliance with that requirement, the defendant submitted a revised water management plan to the prosecutor on 30 June 2008. That plan made no reference to the Pipeline or the monitoring of water at its discharge point.
24 While the underground intake point of the Pipeline is within the area covered by EPL 395, the discharge point is not. It has not been a licensed discharge point under any environment protection licence.
25 From the time of acquiring the Newstan Colliery, the defendant embarked upon a process of site and process improvement. Prior to the incident giving rise to the present offence, it had commenced expanding existing sediment dams as well as improving pumping infrastructure in order to reduce the likelihood of discharge from those dams. In addition, it had undertaken the works previously mentioned of establishing new facilities for the above ground storage of coal fines. Not only did that involve the establishment of storage facilities, as such, but also facilities enabling the separation of solids from water in slurry, thereby reducing the volume of material pumped for underground storage or disposal. Surface water management structures were also established.
26 On 19 April 2009, longwall mining at the Newstan Colliery ceased. In the following month, the colliery was placed on a care and maintenance regime.
The pollution incident
27 At about 8:30 am on 18 August 2008, an employee of the defendant reported that dirty water was flowing in the unnamed creek or tributary of Stony Creek. That dirty water was observed to be flowing from the discharge point of the Pipeline into the creek. The discharge of dirty water continued until the afternoon of 22 August 2008.
28 The plume of dirty water was observed on 18 August to extend for a distance of between 800 and 900 metres downstream from the Pipeline discharge point. The water was dark grey to black in colour, the depth of that colour becoming less as the plume extended downstream. Over the ensuing days the discolouration receded upstream, with the water gradually becoming grey and then brown as the sediments settled within the creek.
29 Although accurate calculation of the volume of material discharged is not possible, the defendant accepts that over the period from 18 to 22 August, somewhere between 1.4 megalitres and 1.8 megalitres of sediment-laden water discharged from the Pipeline into the creek. It is also estimated and accepted by the defendant that somewhere between 6 tonnes and 14.6 tonnes of sediment were contained within the water that was discharged.
30 At the point at which the Pipeline discharged to the unnamed creek, the creek was approximately 3 metres wide. About 20 metres downstream, the creek broadened into a wetland area of about 2 hectares. This area contained a vegetation community identified as Swamp Sclerophyll Forest on Coastal Floodplains which is an endangered ecological community within the meaning of the Threatened Species Conservation Act 1995. The dark grey to black plume within the creek extended into and through this wetland area. Beyond the wetland the sediment-laden waters were observed to extend to the confluence of the unnamed creek with Stony Creek and for a further distance downstream of that point.
31 It is accepted by the parties that, in time, most of the particulate matter discharged from the Pipeline settled from the water body within the 20 metre section of the creek below the discharge point and in the wetland area. These two elements of the creek acted as a trap for the bulk of that material. The consequence was that in the 20 metre section of creek below the discharge point, sediments of up to 40 centimetres in depth were measured while in the wetland area the depth of settled sediment was between 5 and 20 centimetres.
32 As would be apparent, discharge from the Pipeline into the unnamed creek occurred because the level of groundwater within the old mine workings rose above the invert level of the Pipeline. However, the cause of the sediment content carried by that water is not known. The defendant suggests and the prosecutor accepts that it may have occurred by reason of "a geological event" that occurred in the underground workings at the colliery. One such event posited by the defendant is the collapse of a roof or pillar in the old mine workings, resulting in coal particles becoming suspended in the groundwater. Monitoring records kept by the defendant show that the groundwater level had been above the invert level of the Pipeline since February 2008.
Response to the incident
33 Upon discovery of the dirty water discharge into the unnamed creek, the defendant's response was both immediate and, as the prosecutor accepts, appropriate. The defendant immediately commenced water quality monitoring at a location upstream of the discharge point and also at two locations downstream of that point. Having assessed that the source of dirty water was at the inlet to the Pipeline, pumping of decant tailings water into the underground workings ceased and measurement of underground water levels was undertaken. As a result of these measurements, the nearby pump was operated in an endeavour to lower the level of groundwater in the old mine workings. This pump was operated at its maximum rate of 288,000 litres per hour.
34 Shortly prior to midday on 18 August, a senior environmental officer in the employ of the defendant notified the prosecutor of the incident. Later that same day the Department of Primary Industries was notified for the purpose of arranging a meeting between officers of that Department and employees of the defendant to discuss measures appropriate to address remedial action.
35 On 19 August, employees of the defendant met with officers of both the prosecutor and the Department of Primary Industries. Together they made inspections along the unnamed creek from the Pipeline discharge point down to the confluence of the creek with Stony Creek and beyond in order to observe the extent of the pollutant plume. Discussion was also had with those officers as to the most appropriate means of managing and ultimately abating the discharge.
36 On 20 August 2008, the defendant sought expert assistance from GHD, consulting engineers, to formulate mitigation and clean-up strategies. That initial consultation was followed by a visit to the site by experts from that organisation where strategies were formulated and those strategies discussed with officers of the prosecutor. Equipment necessary to implement those strategies was identified and on 21 August both mitigation and clean-up works commenced. These involved the construction of a temporary weir, installation of sediment fences and the use of a "sucker truck" to remove dirty water. Some 82 local residents were also advised by letterbox drop of what had occurred and of the measures being taken to address the problem. The local government authority responsible for the area, namely Lake Macquarie City Council, was similarly advised.
37 As I have earlier indicated, discharge of dirty water from the Pipeline continued until 22 August. The defendant proceeded with mitigatory, clean-up and rehabilitation works until 21 November 2008. During this time, local residents, Lake Macquarie City Council and the prosecutor were kept abreast of progress. Following an inspection of the area by officers of the prosecutor on 25 November 2008, the defendant was advised that both clean-up and rehabilitation works had been satisfactorily undertaken, with the result that no further work was required. A final letter box drop to local residents in January 2009 confirmed that work was complete.
Observations and measurements
38 When the unnamed creek was inspected on 19 August by Hamish Rutherford, an officer of the prosecutor, he observed that in the vicinity of the Pipeline discharge point the sediment-laden water was black-grey in colour and had an appearance consistent with suspended coal fines. The dark grey to black turbid plume then observed by Mr Rutherford extended approximately 5 metres upstream of the discharge point as well as a considerable distance downstream. About 5 metres downstream from the discharge point Mr Rutherford placed his hand into the waters of the creek and upon removal observed that his hand was covered in fine black sludge. Near to the edge of the creek he was able to feel a layer of fine sludge on the creek bed which, when scooped to the surface, showed it to be a fine black sludge similar to the material suspended in the waters of the creek.
39 Mr Rutherford returned to inspect the creek on 21 August. Observation of the creek proximate to the discharge point of the Pipeline revealed a plume of similar colour to that which had been observed on 19 August although of a slightly lighter shade. It was also observed that the water level in the creek had reduced by between 5 and 10 centimetres, leaving a thin layer of black sludge material on the creek bank.
40 When Mr Rutherford returned on 25 August he observed that the waters of the creek in the vicinity of and downstream of the discharge point appeared to be relatively free of turbidity, unlike the position that pertained on his prior visits. He was able to observe the bed of the creek and noted that a black sediment had settled over it.
41 In the period during which the discharge from the Pipeline into the creek was closely observed, a number of water samples were taken both by the defendant and by the prosecutor. These samples were subjected to laboratory testing and the results made known by each party to the other. There is no issue between the parties as to these results.
42 Relevantly, the defendant sampled water in the creek upstream of the discharge point as well as a short distance downstream from that point on each of 18, 19 and 20 August. The prosecutor sampled at about the same points on 19 December. As would be apparent, the upstream point was selected to provide background levels in the creek, unaffected by the discharge from the Pipeline. Among the measurements to which each sample was subjected were measurements for both total suspended solids (TSS) and turbidity (expressed as NTU). A table reflecting the results for those analytes appears below -
Analyte Site Newstan DECC
18 - 20 Aug 08 19 Aug 08
Range Median
TSS Upstream 16 - 150 19 16
(mg/L)
Discharge
location /5m 414 - 6000 922 850
downstream
Turbidity Upstream 20 - 81 23 26
Discharge
(NTU) location /5m 315 - 3990 774 750
downstream