Environmental harm
5The Prosecutor read the affidavit of Dr Ling, senior environmental scientist, Office of Environment and Heritage, dated 21 February 2012. Dr Ling has expertise in wetland ecology including monitoring and assessment of wetlands using aquatic macroinvertebrates and plants. Her expertise does not extend to fish sensitivities to fine sediments. Dr Ling was asked in August 2011 to provide her expert opinion on the environmental impacts of the discharge of approximately 1 - 2ML of sediment laden water from erosion and sediment control structures on the Ravensworth property into Bowmans Creek. Dr Ling did not attend the property and relied on a sample taken by officers of the Office of Environment and Heritage on 19 March 2011, a report by the Defendant dated 24 March 2011, and photographs taken at the property. Dr Ling states that the analysis of water samples suggests that there was significant unnatural discharge of sediment.
6Dr Ling did not believe that any samples were taken or data recorded about any impact of the discharge on the flora or fauna of the site. After investigating the Office of Environment and Heritage's databases and conducting a literature search of ecological studies, Dr Ling compiled a list of potential aquatic flora and fauna recorded in the vicinity of Bowmans Creek. No species of fish or aquatic macroinvertebrates listed under the Fisheries Management Act 1994 or the Environment Protection and Biodiversity Conservation Act 1999 (Cth) were recorded.
7Attached to Dr Ling's affidavit is a table of macroinvertebrates and aquatic vegetation that would have been most affected by the discharge in her opinion. She identified the immediate potential impacts of fine sediment on aquatic flora and fauna. The fine sediment would result in reduced light and subsequently reduced photosynthesis for any submerged vegetation. If the increase in turbidity was only for a short period, with follow-up flushing of the sediment with freshwater, the effect on submerged vegetation would have been minimal. If the affected area was not flushed with fresh water, the smothered flora and fauna would have started to decompose, seriously affecting water quality. The fine sediment may have smothered and killed, or affected the ability of many macroinvertebrates to uptake oxygen. The short and long term effects of the sediment on macroinvertebrates depends on the follow-up flushing and the duration the fine sediment was in the water. Animals such as fish and turtles may have been affected by the reduction in abundance of their food source. Native fish may have had difficulty breathing with suspended solids in the water column.
8Over a long period of time, sediment covering plants and other natural substrates can result in reduced invertebrate richness and density, and alteration of species composition. Excessive sedimentation affects the invertebrates by burying essential detrital (rock particles) and algal food sources, reducing flow of interstitial water necessary to supply dissolved oxygen, and killing macrophytes (aquatic plants) that provide attachment structures and shelter to the invertebrates. Resuspension of deposited sediment through mixing induced by surface wind or fish such as carp can further damage invertebrate communities. Smothered organisms and vegetation would then decompose, resulting in low water quality.
9The long term effects on flora and fauna in the area depend on how much, and how long, fine sediment will remain in the system; and the likelihood, amount, and length of time of resuspension. In Dr Ling's expert opinion, the release of sediment laden water was likely to have resulted in immediate short term harm to wetland fauna and flora immediately downstream of the discharge point. The resilience of flora and fauna would have been likely to aid recovery if the impact was mitigated by flushing or not repeated.
10The Defendant relied on an affidavit of Dr Lincoln Smith, aquatic ecologist director of Cardno Ecology Lab. Dr Lincoln Smith is familiar with Bowmans Creek having previously undertaken ecological studies in the Creek in 2006 and 2010. The results of the water sampling data collected by Ravensworth establishes that there was a large pulse of highly turbid water caused by high concentrations of total suspended solids (TSS) in water entering Bowmans Creek between the upstream and downstream water sampling positions. Its extent is unknown. On 17 March 2011 the TSS concentration downstream in Bowmans Creek was 1,690mg/L. By the next day the TSS of water sampled downstream had fallen to a concentration of 111mg/L, and 32mg/L the following day. The upstream readings were 23 (17 March), 56 (18 March) and 7 and 9 (19 March) respectively. He considered the water quality data was inadequate as scientific data as it was unreplicated and more sampling should have been done at multiple sites from the discharge point into Bowmans Creek to its confluence with the Hunter River. No information on the extent of sedimentation within the Creek was obtained. The downstream extent of sediment deposited does not appear to have been measured with accuracy. No biological data was collected which would have provided some indication of ecosystem health to be determined.
11Rainfall data was also assessed. Dr Lincoln Smith considered that it was possible a second rain event upstream would have helped flush out any residual water from the incident. Dr Lincoln Smith went on a site visit on 30 May 2012. General observations of the Creek did not reveal any apparent residual effects from the discharge associated with the incident, such as large deposits of sand. He considered that the extent of actual harm was some physical harm through short term increase in TSS and a poorly understood degree of sedimentation which was probably flushed away by June 2011 and certainly by May 2012.
12It was likely there was potential for harm but the extent of this harm was considered comparatively trivial in the context of the existing environment given the short timeframe of the discharge, the limited spatial and temporal extent of the disturbance, and the nature of the discharge. There was no information to suggest the sediments were contaminated with toxic chemicals. The potential for smothering of the creek bed with loss of habitat and potential clogging of sensitive gills or filter-feeding organs of aquatic fish and invertebrates existed but the sediment particles appeared very fine and alluvial, and therefore likely to have caused less impact.
13Dr Lincoln Smith did not agree with all aspects of Dr Ling's report. The very high reading of 4,540mg/L was taken in the gully 20m from Bowmans Creek. This can be contrasted with 1,690mg/L measured downstream in Bowmans Creek. These samples represent different environmental conditions and should not be considered as replicates. Dr Lincoln Smith agreed that there was an immediate increase in TSS below the discharge point but the sampling regime did not enable an assessment of long term impacts. There is no data on the extent of deposition of sediment at the site, requiring assumptions about the spatial and temporal extent of deposition. In relation to predicted impacts, Dr Lincoln Smith considered the potential for reduced light, and therefore photosynthesis for submerged vegetation, was unlikely to have occurred as a result of the incident given the short term nature of the disturbance. Dr Lincoln Smith considered there was some evidence that some habitat was smothered but no evidence that invertebrates were, so that Dr Ling's statement suggesting they would have been was speculative. Further there was no evidence of the spatial and temporal extent of deposition. There was no evidence of fish or turtle kills as a result of the incident. There was no evidence to support Dr Ling's statement that any sedimentation that might have occurred was excessive.
14In cross-examination Dr Lincoln Smith agreed that his statement in his report that more sediment may have been collected in the gully which had exposed dirt likely to be eroded and transported into Bowmans Creek meant there was a likelihood that more sediment could have been collected between the point of the high reading sample in the gully and Bowmans Creek.
15The Defendant also read the affidavit of Mr O'Brien, General Manager, Environment and Community of the Defendant's parent company, Xstrata Coal NSW (Xstrata), dated 5 July 2012. There was an environmental management system in place on 17 March 2011. A key part of that was the erosion and sediment control plan, the purpose of which included:
(a)to identify activities that could generate sediment
(b)to describe the location, function and capacity of sediment control
(c)structures required to minimise soil erosion and the potential for sediment downstream
(d)to ensure erosion and sediment control structures are appropriately maintained
(e)to meet the requirements of the EPA publication NSW Managing Urban Stormwater: Soils and Construction (known as the blue book)
16The following processes were in place before the incident to prevent it from occurring:
(a)requiring a contractor to have a ground disturbance permit for works on site issued by Ravensworth to ensure that the blue book requirements were met, and having a site surveyor check this permit
(b)requiring a work authorisation for a contractor to work on site, and ensuring that the contractor had completed the appropriate inductions
(c)completion of a safe work method statement or risk assessment before any work
(d)inspections of structures according to defined intervals
17The incident occurred despite the above processes primarily due to:
(a)confusion on behalf of the contractor carrying out the works as to the status of the diversion drain and the change in surface water classification running into that drain
(b)failure to comply with the sediment and erosion control plan
(c)failure to follow the work authorisation/ground disturbance permit process
(d)inadequate supervision by Ravensworth's personnel of contractors on site
18Mr O'Brien agreed with the incident cause analysis method (ICAM) (SOAF par 26) document (prepared six days after the incident) that non-compliance with, and deficiencies in, the environmental management system were causal factors.
19Immediately after Ravensworth's personnel became aware of the pollution incident on 17 March 2011, it acted without delay to control the pollution and prevent further discharge of water from the premises. The mine manager and mining superintendent immediately went to the location of the incident. They made arrangements to stop the flow of sediment laden water down the clean water diversion drain into Bowmans Creek and divert the water into the 1000ML dam. Mr Newton, Environment and Community Coordinator at Ravensworth, then took samples and photographs of the flow path of the discharge in the sediment and within Bowmans Creek. The samples were sent to a laboratory for testing.
20Mr O'Brien and Ravensworth regret that the incident occurred. Mr O'Brien has overseen actions aimed at ensuring that this incident does not recur. In the days immediately following the incident Ravensworth reviewed drainage structures at the mine site to verify integrity and compliance with the erosion and sediment control plan, took additional water samples upstream and downstream of the entry point 24 and 48 hours after the incident, and communicated the incident to other Xstrata sites in NSW. Ravensworth also took numerous actions to prevent such an incident from occurring by addressing the deficiencies in the environmental management system. The total expenditure in response to the incident was approximately $1.35M. Ravensworth also developed a water management permit system requiring approval from the mine manager before any pump or pipeline works are undertaken on site. Ravensworth's personnel have undergone training aimed at greater oversight and control of contractor authorisations and the importance of adhering to the work authorisation process.
21Mr O'Brien states that Ravensworth has a good environmental performance record and refers to a guide relating to erosion and sediment control developed by Xstrata to guide its operations. He also identifies numerous contributions Xstrata has made to community initiatives in the Hunter Region since 2008, including funding the Hunter Central Rivers Catchment Management Authority's Wybong Catchment Improvement Project and the Hunter River Rehabilitation Project.